Can not edit any post, page or load admin setup screen

I have WPMUDEV on my site for a long time, I haven't changed anything. But now nothing on my site will work. I can't access the dashboard without a warning:
"Cannot load wpmudev-support."
If I try to edit or add a new post I get this:
"Invalid post type."
If I try to add a profile I get this:
"Sorry, you are not allowed to edit posts in this post type."
I have the same issue as here:
I have deactivated Defender but that did not fix the issue.