As soon as I try to update X from 8.0.11 to 8.1.3. I got the following error:
There was a critical error on your website. Please check the inbox of your website administrator email address for further instructions.
Ein Fehler vom Typ E_ERROR wurde in der Zeile 55 der Datei /home/travelth/mysite.com/wp-content/themes/x/framework/functions/x/validation/class-validation-cornerstone.php verursacht. Fehlermeldung: Uncaught Error: Call to undefined method TGM_Plugin_Activation::is_plugin_activated() in /home/travelth/mysite.com/wp-content/themes/x/framework/functions/x/validation/class-validation-cornerstone.php:55
#0 /home/travelth/mysite.com/wp-includes/class-wp-hook.php(287): X_Validation_Cornerstone->maybe_show_notices(’’)
#1 /home/travelth/mysite.com/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(’’, Array)
#2 /home/travelth/mysite.com/wp-includes/plugin.php(484): WP_Hook->do_action(Array)
#3 /home/travelth/mysite.com/wp-admin/admin-header.php(292): do_action(‘admin_notices’)
#4 /home/travelth/mysite.com/wp-admin/update-core.php(979): require_once(’/home/travelth/…’)
I also deleted X and Cornerstone manually and uploaded the newest version via FTP. But I got the same error. Cornerstone is ok, but as soon as I update X I got the critical error.
What can be the reason for this and how can I fix it?