XF 2.1 Don't see threads after move into another forum

[ShinLim]

I chose many threads, and then I moved them to another forum, but after that i re-check and I don't see those threads in that forum (but threads still exist)
I don't know why, but after I setup in "Thread list date limit" (in Nodes) to 1 year, those threads are appear
Anyone meet this issue like me ? I've never meet this situation before because i just upgraded to XF 2.1x

 

[ShinLim]

Edit: Problem has been fixed by Rebuild Search Index
For anyone meet this issue like me will know how to deal with this