For the last two or three days I've encountered a strange issue with the forum listing page here. It's intermittent but I can generally replicate it more often than not.
I'm using Windows 11 latest build, Firefox 148.0 (64bit) with a cleared cache.
There's been a similar problem here for some time now but I've personally not seen it on other Xenforo based forums. The common factor appears to be Firefox.
[EDIT] There also appears to be an issue here with linking posts. I attempted multiple times to link other posts detailing the same issue but gave up in the end.
In short you are not alone but there is no fix as yet.
A user group permissions were set wrong. People assigned to this user group were supposed to be prevented from posting on a specific forum. By accident, it was set for them to not be able to view all forums.
I haven't found anybody I can blame for the mistake yet, but I'm still looking.