505 errors on all plugins and themes

Hello, I have a 505 error on attempt to install all plugins and themes. Tried disabling all plugins other than WPMU but no luck.

  • Dimitris
    • Support Star

    Hey there Nick,

    hope you're doing good and thanks for joining us! :slight_smile:

    First of all, I'd like to mention that I tried to install couple of our plugins via WPMUDEV Dashboard in a test WP Engine site and I had no troubles with that.

    Now, inspecting your website I was able to see this error in action and WP Engine error logs revealed the following:
    PHP Fatal error: Class 'WP_Ajax_Upgrader_Skin' not found in /nas/content/live/xxxxxxxxx/wp-content/plugins/wpmudev-updates/includes/class-wpmudev-dashboard-upgrader.php on line 634, referer: https://xxxxxxxxx.wpengine.com/wp-admin/admin.php?page=wpmudev-plugins

    The WP_Ajax_Upgrader_Skin class is part of WP core though, as you can also see here:

    Could you please try to update WP core files? You can do so manually, by downloading WordPress from here, then extract compressed file locally and upload all folders and files apart from /wp-content/ in the root folder of your installation via FTP. Please keep a backup of your website prior to that, just in case something goes wrong and you have to restore.
    Reference: https://codex.wordpress.org/Updating_WordPress#Manual_Update

    You may also want to contact WP Engine about this as they provide pre-installed WordPress instances and may provide an easier way to update or even do that for you.

    Let me know how that goes!
    Warm regards,

  • Nick
    • New Recruit

    Thank you, I did go through the process you outlined. Now I get:

    5 PHP Fatal error: Class 'WP_Ajax_Upgrader_Skin' not found in /nas/content/live/bmpfilmco/wp-content/plugins/wpmudev-updates/includes/class-wpmudev-dashboard-upgrader.php on line 634

  • Adam Czajczyk
    • Support Gorilla

    Hello Nick!

    The site that's assigned to this thread is still running on WP 4.4.8 which is pretty outdated. The "WP_Ajax_Upgrader_Skin" class was introduced with WP 4.6 so the solution here is to update WordPress.

    Update to 4.6 release should help but event then I would strongly recommend moving to the newest release (4.7.3) as it carries out some very important security patches. Would that be possible?

    Best regards,

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