"Our second AP is working fine with same setting we are not getting any broadcast coming from it. "
What firmware is it running I know you said that the one that is not working is running 11.21 but what about the one that is working ? If it is a different version then try it on the other AP and see if that resolves the issue.
If it does not then I would try a full reset (same as password recovery technique) and then test again
11.21 is a little older now, I am not one that says upgrade for the sake of upgrading but in WLAN it pays to be on the latest or near to the latest, the main driver for this is the advances in security features