It is like the 5GHz network might not be properly routed or the DHCP settings could be misconfigured. You could try checking the DHCP settings in the OC200 controller and make sure the 5GHz network is set up to obtain an IP address correctly. Additionally, it might help to reboot the APs and the controller. Let me know how it goes more info.

I have the same problem on a fairly regular basis. On my EAP620 HD, the 5 gHz network will suddenly have no Internet connection. The 2.5 gHz side works fine.

Nothing changes in the configuration during these episodes. I'm 20 feet with a clear line of sight to the AP, and the computer shows full signal.

I used to be able to reset the AP using the TP-Link application; but now, despite the computer being connected to the AP, the app can't find it.

The AP is mounted on a wall behind a projection screen, so continually having to take it down and press a button on it is not an acceptable "solution."