It seems like Tapatalk has all kinds of issues with the forum.
I've checked it out on the Tapatalk website, and it seems like this issue pops up every once in a while. The problem is in the app itself, which I have no control over, and the guys in the support forum on the Tapatalk website can't seem to figure out what's going on.
https://support.tapatalk.com/
Now The "Participated" Section Isn't Showing The Threads