forum cache not auto update
 

So whenever, I add someone into a usergroup. I have to manually clear the forum cache, how do I fix this issue?

Why do you have to do that? What happens if you don't?

If I don't nothing updates, like if I add someone to the usergroup, they don't show up on "Show Team" Clear forum cache, it works.

Do you mean "View Site Leaders"? That page is cached and has a pretty long timeout by default. If that's the only thing that doesn't update, and you really need it to update faster, you can change the cache setting at Server Settings and Optimization Options > Forum Leaders Cache. (or set it temporarily to 0 and see if that solves the problem).