Finally I found a way to solve this problem, while desperately waiting for help from this forum and local partner.
Here is the step I've done :
- deleted the vlan that used by down AP .
- re add the vlan
- re add the IP address
- last, this is when I realize what the problem truly are. Check in the Configuration Advanced Services > Redundancy, your controller operational state in every subnet and vlan use for AP management. In my current environment. We have 3 subnet for 3 different region. Turns out one from three subnet in our master controller operational state as BACKUP. And cause all the RAP under the subnet down. maybe because the secondary contoller didn't accept the AP, because the master is UP.
After knowing the vlan redundancy operational state is BACKUP, I deleted it from virtual routing table. And suddenly it's reappear and stated as MASTER. No need to re add the vlan in the redundancy virtual router table.
That's it, and problem solved.
Cheers.