@McLeeland 

I, too, also have an OC200, SG2008P, but an ER605v1. I currently have a site where the OC200 cannot re-adopt the ER605 since it updated to 5.12.9 - and the location is a 3 hour drive away so I am not able to physically reboot it or troubleshoot. One of my other sites re-adopted the ER605 without a problem after updating the OC200 to 5.12.9. At my home, I had to physically reboot the ER605 because it failed to re-adopt after updating the OC200.

In times past, I have had to reset the ER605 to default. When the OC200 sees it, and I select "adopt," it will reload the settings on the ER605.

Ever since I installed Omada SDN I've almost always encountered issues with the OC200 failing to re-connect to the ER605 after the controller is updated.

  @Omada_Armada 

At least I only have to go downstairs to access mine :)

Update on my situation: During the weekend I tried downgrading the firmware on both the OC200 and ER605. For some reason the version I got throught the UI was newer than what was officially available on the support page for the respective devices. A little bit of a red flag there. Not that it did any good. I reset all three and even tried the ER605 in standalone mode with same results - it can get a public IP and gateway from my ISP/modem and even claims to be connected, but cannot "forward" that connection to my LAN or even to itself to get the time and date from an NTP server. As if that wasn't bad enough the OC200 is now dead. Can't even get it into recovery mode when connected straight to a PC.

So I'm calling it quits and RMAing them both.