Mailchimp throwing white page error

I have a white page problem with mailchimp.

Error log:

~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/A0383E2A-0041-4636-BBC8-3776C6550DBE/error.log:19588: [Wed Feb 21 13:39:57.822678 2018] [:error] [pid 14647] [client 2001:16b8:2b75:5100:41d4:bd64:8dd7:9bcc:54856] PHP Fatal error:  Uncaught exception 'Exception' with message 'Invalid MailChimp API key supplied.' in /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/vendor/drewm/mailchimp-api/src/MailChimp.php:39\nStack trace:\n#0 /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/PerchMailChimp_Factory.class.php(22): DrewM\\MailChimp\\MailChimp->__construct('')\n#1 /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/PerchMailChimp_Campaigns.class.php(58): PerchMailChimp_Factory->get_api_instance()\n#2 /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/PerchMailChimp_Import.class.php(25): PerchMailChimp_Campaigns->import_next(Object(PerchMailChimp_Import))\n#3 /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/PerchMailChimp_Campaigns.class.php(51): PerchMailChimp_Import->run()\n#4 /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/modes/campaigns.pre.php(31): PerchMailChimp_Campaigns->import()\n#5 /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/_default_index.php(18):  in /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/vendor/drewm/mailchimp-api/src/MailChimp.php on line 39, referer: https://test.sthoerfunk.de/perch/addons/apps/perch_mailchimp/subscribers/

~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/A0383E2A-0041-4636-BBC8-3776C6550DBE/error.log:21210: [Wed Feb 21 14:05:59.332760 2018] [:error] [pid 14675] [client 2001:16b8:2b75:5100:41d4:bd64:8dd7:9bcc:55369] PHP Fatal error:  Class 'DrewM\\MailChimp\\Exception' not found in /var/www/homepage.d/test/perch/addons/apps/perch_mailchimp/lib/vendor/drewm/mailchimp-api/src/MailChimp.php on line 177, referer: https://test.sthoerfunk.de/perch/core/settings/

Strange thing is that on a different Server all works good. So the API Key is good

Here is the Diagnostic Info:

Perch information

Perch: 3.0.14
Production mode: Development (10)
Installed apps: content (3.0.14), assets (3.0.14), categories (3.0.14), perch_blog (5.6.1), perch_events (1.9.5), perch_mailchimp (3.1)
DB driver: PDO
DB tables: perch2_blog_authors (8), perch2_blog_categories (17), perch2_blog_comments (0), perch2_blog_index (63834), perch2_blog_posts (1764), perch2_blog_posts_to_categories (1221), perch2_blog_posts_to_tags (576), perch2_blog_sections (10), perch2_blog_tags (36), perch2_blog_webmention_queue (0), perch2_blogs (1), perch2_categories (15), perch2_category_counts (15), perch2_category_sets (1), perch2_content_index (1336), perch2_content_items (327), perch2_content_regions (14), perch2_events (168), perch2_events_categories (5), perch2_events_to_categories (145), perch2_gallery_albums (1), perch2_gallery_image_versions (18), perch2_gallery_images (3), perch2_mailchimp_campaigns (0), perch2_mailchimp_imports (1), perch2_mailchimp_lists (0), perch2_mailchimp_subscribers (0), perch2_mailchimp_subscriptions (0), perch2_mailchimp_webhooks (0), perch2_members (1), perch2_members_forms (1), perch2_members_member_tags (0), perch2_members_sessions (1), perch2_members_tags (0), perch2_menu_items (11), perch2_navigation (0), perch2_navigation_pages (0), perch2_page_templates (2), perch2_pages (23), perch2_podcasts (2), perch2_podcasts_downloads (0), perch2_podcasts_episodes (3), perch2_resource_log (12771), perch2_resource_tags (75), perch2_resources (8668), perch2_resources_to_tags (284), perch2_settings (56), perch2_user_passwords (1), perch2_user_privileges (52), perch2_user_role_privileges (36), perch2_user_roles (3), perch2_users (9)
Users: 9
App runtimes:
<?php
    $apps_list = [ 
        'perch_blog',
        'perch_events',
        'perch_mailchimp',
    ];
Scheduled tasks for perch_blog: delete_spam_comments (1440 mins), publish_posts (1 mins), process_webmentions (1 mins)
Scheduled tasks for perch_mailchimp: import_data (1 mins)
Editor plug-ins: ckeditor, tinymce
H1: 225eb4eaa1fbb5e389a5273af31edc29
L1: b91f96b0eb1406eb2ae5d148f801b675
F1: 9fab42554990d2c203d599a6437edd2a
headerColour: #1d7eb5
content_singlePageEdit: 1
helpURL:
hideBranding: 1
content_collapseList: 1
lang: de_de
update_2.3.2: done
latest_version:
headerScheme: dark
siteURL: https://test.sthoerfunk.de
dashboard: 0
content_hideNonEditableRegions: 0
logoPath: /perch/resources/sflogoblauorange.png
perch_blog_post_url: /blog/post.php?s={postSlug}
perch_blog_update: 5.6
perch_blog_slug_format: %Y-%m-%d-{postTitle}
perch_blog_akismet_key:
perch_blog_max_spam_days: 0
perch_blog_comment_notify: 0
on_sale_version:
update_2.4.5: done
content_frontend_edit: 0
perch_gallery_update: 2.8.4
perch_events_update: 1.8
perch_members_login_page: /members/login.php?r={returnURL}
perch_events_detail_url: /termine/event.php?event={eventSlug}
perch_gallery_bucket_mode: dynamic
perch_gallery_bucket: gallery_images
perch_gallery_basicUpload: 0
update_2.4.8: done
hide_pwd_reset: 0
update_2.4.9: done
update_2.5: done
update_2.5.1: done
update_2.5.4: done
update_2.6.3: done
update_2.6.5: done
update_2.8.31: done
perch_blog_site_name:
update_2.8.32: done
update_3.0.14: done
perch_mailchimp_api_key: c4f3e30eed0d19680af66916f634df77-us17
perch_mailchimp_campaign_url: /mailchimp/campaign/{campaignSlug}
sidebar_back_link: 0
keyboardShortcuts: 0
content_skip_region_list: 0
assets_restrict_buckets: 0
perch_blog_webmention_tx: 0
perch_blog_webmention_rx: 0
perch_mailchimp_secret: 468de1c
PERCH_DEVELOPMENT: 10
PERCH_STAGING: 50
PERCH_PRODUCTION: 100
PERCH_DB_USERNAME: perch_test
PERCH_DB_SERVER: localhost
PERCH_DB_DATABASE: perch_test
PERCH_DB_PREFIX: perch2_
PERCH_TZ: Europe/Berlin
PERCH_EMAIL_FROM: iphone@sdb-grafik.de
PERCH_EMAIL_FROM_NAME: Matthew Owen
PERCH_LOGINPATH: /perch
PERCH_PATH: /var/www/homepage.d/test/perch
PERCH_CORE: /var/www/homepage.d/test/perch/core
PERCH_RESFILEPATH: /var/www/homepage.d/test/perch/resources
PERCH_RESPATH: /perch/resources
PERCH_HTML5: 1
PERCH_DEBUG: 1
PERCH_FEATHERS: 1
PERCH_PRODUCTION_MODE: 10
PERCH_YOUTUBE_API_KEY: AIzaSyAk9iuNItv7jrZ0iu_O-aYjT-QQFSapfrk
PERCH_RUNWAY:
PERCH_ERROR_MODE: DIE
PERCH_DATE_LONG: %d %B %Y
PERCH_DATE_SHORT: %d %b %Y
PERCH_TIME_SHORT: %H:%M
PERCH_TIME_LONG: %H:%M:%S
PERCH_RUNWAY_ROUTED:
PERCH_STRONG_PASSWORDS:
PERCH_ASSET_VERSION: f704e7442d11292c99b5
PERCH_PREVIEW_ARG: preview
PERCH_TEMPLATE_PATH: /var/www/homepage.d/test/perch/templates
PERCH_TEMPLATE_FILTERS:
PERCH_DEFAULT_DOC: index.php
PERCH_DEFAULT_EXT: .php
PERCH_XHTML_MARKUP:
PERCH_RWD: 1
PERCH_HTML_ENTITIES:
PERCH_SSL:
PERCH_STRIPSLASHES:
PERCH_PROGRESSIVE_FLUSH: 1
PERCH_PARANOID:
PERCH_FORCE_SECURE_COOKIES:
PERCH_DEFAULT_BUCKET: default
PERCH_TRANSLATION_ASSIST:
PERCH_PASSWORD_MIN_LENGTH: 6
PERCH_MAX_FAILED_LOGINS: 10
PERCH_AUTH_LOCKOUT_DURATION: 1 HOUR
PERCH_VERIFY_UPLOADS:
PERCH_PRIV_ASSIST:
PERCH_CUSTOM_EDITOR_CONFIGS:
PERCH_ENABLE_EXIF: 1
PERCH_AUTH_PLUGIN:
PERCH_DB_CHARSET: utf8
PERCH_DB_PORT:
PERCH_DB_SOCKET:
PERCH_APPS_EDITOR_PLUGIN: markitup
PERCH_APPS_EDITOR_MARKUP_LANGUAGE: markdown
Hosting settings

PHP: 5.6.23-0+deb8u1
Zend: 2.6.0
OS: Linux
SAPI: apache2handler
Safe mode: not detected
MySQL client: 5.5.49
MySQL server: 5.5.49-0+deb8u1
Free disk space: 459,77 GB
Extensions: Core, date, ereg, libxml, openssl, pcre, zlib, bcmath, bz2, calendar, ctype, dba, dom, hash, fileinfo, filter, ftp, gettext, SPL, iconv, mbstring, session, posix, Reflection, standard, shmop, SimpleXML, soap, sockets, Phar, exif, sysvmsg, sysvsem, sysvshm, tokenizer, wddx, xml, xmlreader, xmlwriter, zip, apache2handler, PDO, gd, gnupg, intl, json, mcrypt, mysql, mysqli, pdo_mysql, pspell, readline, mhash, Zend OPcache
GD: Yes
ImageMagick: No
PHP max upload size: 256M
PHP max form post size: 256M
PHP memory limit: 1024M
Total max uploadable file size: 256M
Resource folder writeable: Yes
Session timeout: 24 minutes
Native JSON: Yes
Filter functions: Yes
Transliteration functions: Yes
HTTP_HOST: test.sthoerfunk.de
HTTP_COOKIE: __utma=92893080.1564237180.1488376567.1519215389.1519314987.13; __utmc=92893080; __utmz=92893080.1518787764.2.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); PHPSESSID=03me08lfqb0ln8hkmgddmr9a33; cmsa=1; __utma=68138451.1615140241.1488376885.1519296334.1519301161.104; __utmc=68138451; __utmz=68138451.1519028375.89.3.utmcsr=test.sthoerfunk.de|utmccn=(referral)|utmcmd=referral|utmcct=/
HTTP_CONNECTION: keep-alive
HTTP_UPGRADE_INSECURE_REQUESTS: 1
HTTP_ACCEPT: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
HTTP_USER_AGENT: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/604.5.6 (KHTML, like Gecko) Version/11.0.3 Safari/604.5.6
HTTP_REFERER: https://test.sthoerfunk.de/perch/core/settings/diagnostics/
HTTP_ACCEPT_LANGUAGE: en-us
HTTP_ACCEPT_ENCODING: gzip, deflate
PATH: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
SERVER_SIGNATURE: <address>Apache/2.4.10 (Debian) Server at test.sthoerfunk.de Port 80</address>
SERVER_SOFTWARE: Apache/2.4.10 (Debian)
SERVER_NAME: test.sthoerfunk.de
SERVER_ADDR: 2a01:238:422f:9300:9545:a184:58ae:3a16
SERVER_PORT: 80
REMOTE_ADDR: 2001:16b8:2baf:3200:64b0:b318:59af:8750
DOCUMENT_ROOT: /var/www/test
REQUEST_SCHEME: http
CONTEXT_DOCUMENT_ROOT: /var/www/test
SERVER_ADMIN: webmaster@sthoerfunk.de
SCRIPT_FILENAME: /var/www/test/perch/core/settings/diagnostics/index.php
REMOTE_PORT: 54068
GATEWAY_INTERFACE: CGI/1.1
SERVER_PROTOCOL: HTTP/1.1
REQUEST_METHOD: GET
QUERY_STRING: extended
REQUEST_URI: /perch/core/settings/diagnostics/?extended
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php
PHP_SELF: /perch/core/settings/diagnostics/index.php
REQUEST_TIME_FLOAT: 1519317773,642
REQUEST_TIME: 1519317773

I don't find the solution, anybody spot what I may be missing...

thanks!