No valid header

[drbe4t]

Sooo I'm not exactly sure if it's my theme or if it's the plugin but I went to activate it and it said no valid header. Don't know if that's something you are aware of or not.

[Atn-D]

It's also the same problem in all my tests.

[mike42]

Also affected by this- including a bit more information to help you debug.

Environment
Wordpress 3.9, Linux, PHP version not known.

Steps to replicate

1. Log in to admin panel
2. Plugins --> Add new --> Search "Markdown Editor"
3. Click "Install Now" next to "Markdown Editor"

4. Click "Activate"

Expected behaviour
Plugin is activated, returning to the same page.

Actual behaviour
Page hangs on this URL, displaying the message "The plugin does not have a valid header". Plugin is not activated, and "Activate" button becomes hidden.

https://[ site ]/wp-admin/plugins.php?_wpnonce=[ nonce ]&action=activate&plugin=markdown-editor/includes/class-easy-markdown.php

Workaround
After installation, navigate to Plugins --> Installed plugins, and hit "Activate" there instead. This one behaves as expected.