500 Internal Server Error when installing plugins

I just installed the WPMU Dev on my multisite installation, everything worked fine. but when I want to install plugins like WP Smush Pro I get a red bar and error "Server error status: Internal Server Error [500]"

Any ideas?

Thanks in advance for your help,


  • Dimitris
    • Support Star

    Hey there Philipp,

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

    I just accessed your website after you kindly granted support access for us and saw that error message in action.

    Could you please try to deactivate all other plugins, revert to a default theme like TwentySeventeeen and test once more? If this resolves the error, it should be a conflict with some theme and/or plugin(s). Simply activate them back one-by-one checking each time the installation process until you get the 500 error again. Here’s a nice flow chart for a generic conflict test


    If this has no effect, please access your server through FTP, edit the wp-config.php file, find a line like

    define('WP_DEBUG', false);

    and replace it with the following (if the above line doesn’t exist, simply insert next snippet just above the /* That’s all, stop editing! Happy blogging. */ comment)

    // Enable WP_DEBUG mode
    define('WP_DEBUG', true);
    // Enable Debug logging to the /wp-content/debug.log file
    define('WP_DEBUG_LOG', true);
    // Disable display of errors and warnings
    define('WP_DEBUG_DISPLAY', false);
    @ini_set('display_errors', 0);

    Then go ahead and try to replicate the error by installing a plugin from WPMUDEV Dashboard.

    By doing so, a /wp-content/debug.log file should be created.

    Simply download it, rename it to debug.txt and attach it here in your next reply.

    Warm regards,


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