I am pretty certain that this issue is not GeneratePress related, but because your support absolutely rocks I try anyway.
I installed the plugin schema ninja which has a free version and a pro one. To use the free one I had to visit their homepage to get a key for the free version. When I try to authorize it, I don’t get an error message or anything else, the page partially reloads and that’s it. Can this be caused by generatepress or wordpress multisite?
Notice: Undefined variable: post in /home/lolshopc/basketcheck/workinprogress/wp-content/plugins/schemaninja/schema-admin.php on line 133
Notice: Trying to get property ‘ID’ of non-object in /home/lolshopc/basketcheck/workinprogress/wp-content/plugins/schemaninja/schema-admin.php on line 133
That’s the content of line 133: $nonce = wp_create_nonce( 'schema-ninja'.$post->ID );