Hi there,
first up: The site moved a couple times from one provider to the other. These features did work at some point, but after the latest (and hopefully last) move, they aren’t working anymore.
The site in question is http://www.heldenwelt.de/forum
When a user tries to add a topic to his watchlist / subscribe to it, he’ll receive the message: “The selected forum doesn’t exist” (my translation, the English original might be slightly off).
I updated the permalinks structure (of both the forums as well as the normal WordPress) a couple of times. It did work with the “default WP permalinks”, but whenever I switch back to “pretty permalinks”, I receive the error message again.
I checked user permissions and this is not the issue.
Any help would be much appreciated.