I removed the plugin. The problem is sort of resolved now. Thanks
To add some clarity: In my widgets, I also tried setting the standard sidebars to see if they would appear, but they didn’t.
Maybe a clue: I tried every location, and I noticed it will only appear when I set it to the header location (instead of e.g. sidebar top) (Of course this is not the location I want the sidebar). I couldn’t find any relevant differences between the ‘sidebar-top.php’ and the ‘sidebar-header.php’ files.
Thanks for your reply Accu. I checked this. Sadly this was not the solution for me. My sidebar is registered in functions.php and its reference (sidebar-top.php) also seems correct.
I am using Custom Sidebars by WPMU DEV. I believe it is either this update, or the wordpress version update that triggered this problem.
