Excerpt field has disappeared from the blog post edit screen

Hi

The excerpt field has disappeared from my blog posts in the Perch post edit screen.

The excerpt appears on the front end where there a post already had one saved in the database, but I can't add excerpts for new posts, so I don't think it's an issue with my template code.

Any suggestions?

Thanks.

Here's the markup for post_in_list.html:

<perch:before>
    <perch:every nth-child="odd">
        <section class="section section--blog">
            <div class="grid-container">
                <div class="row">
                    <div class="grid-twelve">
                        <div class="section-body">
                            <perch:if exists="featuredimage">
                                <div class="half clearfix">
                                    <a href="<perch:blog id="postURL" />" rel="bookmark" class="entry-title">
                                        <img class="featured-image" src="<perch:blog id="featuredimage" label="Featured Image" type="image" width="700" height="467" crop="true" />" alt="<perch:blog id="postTitle" />" />
                                    </a>
                                </div>
                            </perch:if>
                            <div class="half clearfix">
                                <div class="content-block content-block--left">
                                    <h2><a href="<perch:blog id="postURL" />" rel="bookmark" class="entry-title"><perch:blog id="postTitle" /></a></h2>
                                    <p class="entry-published date intro">Posted: <span><perch:blog id="postDateTime" format="%d %B %Y" /></span></p>
                                    <p class="entry-category">
                                        Category:
                                        <perch:categories id="categories" set="blog" label="Categories" display-as="checkboxes">
                                            <a href="archive.php?cat=<perch:category id="catSlug" type="slug" />">
                                                <perch:category id="catTitle" type="text" /></perch:category>
                                            </a>
                                        </perch:categories>
                                    </p>
                                    <div class="description entry-summary">
                                        <perch:blog id="excerpt" type="textarea" textile="true" />
                                    </div>
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </section>
    <perch:else />
        <section class="section section--white section--blog">
            <div class="grid-container">
                <div class="row">
                    <div class="grid-twelve">
                        <div class="section-body">
                            <div class="half clearfix">
                                <div class="content-block content-block--right">
                                    <h2><a href="<perch:blog id="postURL" />" rel="bookmark" class="entry-title"><perch:blog id="postTitle" /></a></h2>
                                    <p class="entry-published date intro">Posted: <span><perch:blog id="postDateTime" format="%d %B %Y" /></span></p>
                                    <p class="entry-category">
                                        <perch:categories id="categories" set="blog" label="Categories" display-as="checkboxes">
                                            Category:
                                            <a href="archive.php?cat=<perch:category id="catSlug" type="slug" />">
                                                <perch:category id="catTitle" type="text" /></perch:category>
                                            </a>
                                        </perch:categories>
                                    </p>
                                    <div class="description entry-summary">
                                        <perch:blog id="excerpt" type="textarea" textile="true" />
                                    </div>
                                </div>
                            </div>
                            <perch:if exists="featuredimage">
                                <div class="half clearfix">
                                    <a href="<perch:blog id="postURL" />" rel="bookmark" class="entry-title">
                                        <img class="featured-image" src="<perch:blog id="featuredimage" label="Featured Image" type="image" width="700" height="467" crop="true" />" alt="<perch:blog id="postTitle" />" />
                                    </a>
                                </div>
                            </perch:if>
                        </div>
                    </div>
                </div>
            </div>
        </section>
    </perch:every>
<perch:after>

Diagnostics:

Perch: 3.0, PHP: 5.6.37, MySQL: 10.1.31-MariaDB, with PDO
Server OS: Linux, litespeed
Installed apps: content (3.0), assets (3.0), categories (3.0), perch_blog (5.6.1)
App runtimes: <?php $apps_list = array( 'perch_blog', );
PERCH_LOGINPATH: /admin
PERCH_PATH: /home/mreltd/public_html/admin
PERCH_CORE: /home/mreltd/public_html/admin/core
PERCH_RESFILEPATH: /home/mreltd/public_html/admin/resources
Image manipulation: GD
PHP limits: Max upload 512M, Max POST 512M, Memory: 256M, Total max file upload: 256M
F1: 0c66c2e1f82f9e0b7617b2cb8270f2c7
Resource folder writeable: Yes
HTTP_HOST: www.mreltd.co.uk
DOCUMENT_ROOT: /home/mreltd/public_html
REQUEST_URI: /admin/core/settings/diagnostics/
SCRIPT_NAME: /admin/core/settings/diagnostics/index.php