HBOGO on AppleTV Keeps Asking to Activate

I have been trying to access HBOGO on AppleTV. It's been working fine for a month. Now, out of the blue, it keeps giving me an activation code and instructing me to activate. I do so on the the HBOGO activation site - AppleTV as device, XFINITY as provider, it tells me activation is successful. When I hit play on the program, it returns to a new activation screen with a new code, ad infinitum. I've tried unplugging to reset the AppleTV unit, and have tried restarting from the Settings menu. Nothing resolves it. Anyone have a good idea for me? Thanks.