Hi @hamidxazad,
Please got to wpForo > Overview admin page and click the [Soft Flush Permalinks] button, if it doesn’t help then click the [Hard Flush Permalinks] button.
Also, delete all kind of caches.
@hamidxazad,
Try the following steps:
1. Go to wpForo > Tools > Database Tables Tab and make sure there is no any problem
2. Go to wpForo > Tools > Debug > Error & Issues Sub-tab and check the errors.
3. Go to wpForo > Boards and make sure the board with boardid:0 has a pageid.
4. Delete all kind of caches, go to WordPress Settings > Permalinks and click the [Save Changes] button.
5. Disable other plugins for a while, then check the menu. If it works, then activate the plugins one by one and check to find the problem maker.