perch backup app - zero size?

fixed the problem with mysqldump, added the path in settings, but still get the sql dump as zero size?

extended diagnostic info

PERCH INFORMATION

Perch: 2.8.29
Production mode: Production (100)
Installed apps: content (2.8.29), assets (2.8.29), categories (2.8.29), perch_forms (1.8.3), perch_backup (1.2)
DB driver: PDO
DB tables: perch2_categories (0), perch2_category_counts (0), perch2_category_sets (0), perch2_content_index (3), perch2_content_items (2), perch2_content_regions (1), perch2_forms (1), perch2_forms_responses (8), perch2_navigation (0), perch2_navigation_pages (0), perch2_page_templates (0), perch2_pages (1), perch2_resource_log (0), perch2_resource_tags (0), perch2_resources (0), perch2_resources_to_tags (0), perch2_settings (16), perch2_user_passwords (0), perch2_user_privileges (30), perch2_user_role_privileges (16), perch2_user_roles (2), perch2_users (1)
Users: 1
App runtimes:
<?php
    $apps_list = array(
        'content', 
        'categories',
    'perch_forms'
    );
Editor plug-ins: markitup
H1: 421aa90e079fa326b6494f812ad13e79
L1: 4116a07dd766d1183b30811c41d5f94f
F1: 2edba60ed1f613d6dd804feb202456a2
headerColour: #ffffff
content_singlePageEdit: 1
helpURL:
siteURL: /
hideBranding: 0
content_collapseList: 1
lang: en-gb
update_2.8.29: done
latest_version: 2.8.15
on_sale_version: 2.8.29
headerScheme: light
perch_backup_mysqldump_path: /usr/local/mysql/bin/mysqldump
dashboard: 0
hide_pwd_reset: 0
content_hideNonEditableRegions: 0
content_frontend_edit: 0
PERCH_DEVELOPMENT: 10
PERCH_STAGING: 50
PERCH_PRODUCTION: 100
PERCH_DB_USERNAME: root
PERCH_DB_SERVER: localhost
PERCH_DB_DATABASE: uxgent_perch
PERCH_DB_PREFIX: perch2_
PERCH_TZ: UTC
PERCH_EMAIL_FROM: john@uxgent.co
PERCH_EMAIL_FROM_NAME: john griffiths
PERCH_LOGINPATH: /perch
PERCH_PATH: /Users/john/projects/uxgent-perch/htdocs/perch
PERCH_CORE: /Users/john/projects/uxgent-perch/htdocs/perch/core
PERCH_RESFILEPATH: /Users/john/projects/uxgent-perch/htdocs/perch/resources
PERCH_RESPATH: /perch/resources
PERCH_HTML5: 1
PERCH_EMAIL_METHOD: smtp
PERCH_EMAIL_HOST: smtp.mailgun.org
PERCH_EMAIL_AUTH: 1
PERCH_EMAIL_SECURE: ssl
PERCH_EMAIL_PORT: 465
PERCH_EMAIL_USERNAME: postmaster@uxgent.co
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_DEBUG:
PERCH_PREVIEW_ARG: preview
PERCH_TEMPLATE_PATH: /Users/john/projects/uxgent-perch/htdocs/perch/templates
PERCH_DEFAULT_DOC: index.php
PERCH_DEFAULT_EXT: .php
PERCH_PRODUCTION_MODE: 100
PERCH_RWD:
PERCH_HTML_ENTITIES:
PERCH_SSL:
PERCH_STRIPSLASHES:
PERCH_PROGRESSIVE_FLUSH: 1
PERCH_PARANOID:
PERCH_FORCE_SECURE_COOKIES:
PERCH_PASSWORD_MIN_LENGTH: 6
PERCH_MAX_FAILED_LOGINS: 10
PERCH_AUTH_LOCKOUT_DURATION: 1 HOUR
PERCH_VERIFY_UPLOADS:
PERCH_AUTH_PLUGIN:
PERCH_DB_CHARSET: utf8
PERCH_DB_PORT:
PERCH_DB_SOCKET:
PERCH_SESSION_TIMEOUT_MINS: 20
HOSTING SETTINGS

PHP: 5.6.22
Zend: 2.6.0
OS: Darwin
SAPI: fpm-fcgi
Safe mode: not detected
MySQL client: mysqlnd 5.0.11-dev - 20120503 - $Id: 76b08b24596e12d4553bd41fc93cccd5bac2fe7a $
MySQL server: 5.7.13
Free disk space: 213.51 GB
Extensions: Core, date, ereg, libxml, openssl, pcre, sqlite3, zlib, bcmath, bz2, calendar, ctype, curl, dba, dom, hash, fileinfo, filter, ftp, gd, gettext, SPL, iconv, json, ldap, mbstring, session, standard, mysqlnd, odbc, pcntl, mysqli, PDO, pdo_mysql, PDO_ODBC, pdo_sqlite, Phar, posix, readline, Reflection, mysql, shmop, SimpleXML, soap, sockets, exif, sysvmsg, sysvsem, sysvshm, tokenizer, wddx, xml, xmlreader, xmlrpc, xmlwriter, xsl, zip, cgi-fcgi, mhash
GD: Yes
ImageMagick: No
PHP max upload size: 2M
PHP max form post size: 8M
PHP memory limit: 128M
Total max uploadable file size: 2M
Resource folder writeable: Yes
Session timeout: 24 minutes
Native JSON: Yes
Filter functions: Yes
Transliteration functions: No
USER: john
HOME: /Users/john
FCGI_ROLE: RESPONDER
SCRIPT_FILENAME: /Users/john/projects/uxgent-perch/htdocs/perch/core/settings/diagnostics/index.php
QUERY_STRING: extended
REQUEST_METHOD: GET
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php
REQUEST_URI: /perch/core/settings/diagnostics/?extended
DOCUMENT_URI: /perch/core/settings/diagnostics/index.php
DOCUMENT_ROOT: /Users/john/projects/uxgent-perch/htdocs
SERVER_PROTOCOL: HTTP/1.1
REQUEST_SCHEME: http
GATEWAY_INTERFACE: CGI/1.1
SERVER_SOFTWARE: nginx/1.10.1
REMOTE_ADDR: 127.0.0.1
REMOTE_PORT: 59001
SERVER_ADDR: 127.0.0.1
SERVER_PORT: 80
SERVER_NAME: localhost
REDIRECT_STATUS: 200
HTTP_HOST: localhost
HTTP_ACCEPT: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
HTTP_CONNECTION: keep-alive
HTTP_COOKIE: PHPSESSID=pfep0oi6ur3uhjuk93ho6mvfp3; _ga=GA1.1.1234079793.1465655841; cmsa=1
HTTP_USER_AGENT: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/601.6.17 (KHTML, like Gecko) Version/9.1.1 Safari/601.6.17
HTTP_ACCEPT_LANGUAGE: en-us
HTTP_REFERER: https://localhost/perch/core/settings/diagnostics/
HTTP_ACCEPT_ENCODING: gzip, deflate
PHP_SELF: /perch/core/settings/diagnostics/index.php
REQUEST_TIME_FLOAT: 1465862550.7556
REQUEST_TIME: 1465862550

i've enabled debug mode, here's the output on backup:

[16] SELECT * FROM (SELECT DISTINCT settingID, settingValue, userID FROM perch2_settings WHERE userID=1 OR userID=0 ORDER BY userID DESC) AS settings GROUP BY settingID, settingValue, userID
Adding: The checks on the right will show if your MySQL database can also be backed up. If it cannot, you will need to do this another way as all site content is stored in the database.
Queries: 5
Memory: 2.0597

can't see anything much in the nginx access log, should i check anywhere else?