No video through Yamaha receiver

I recently added a new Yamaha RX-A2A receiver to my system. The intended configuration is to connect all video sources into the receiver and a single cable to the TV’s ARC input port. That way I should never have to change the TV source and could change sources and volume using the receiver’s remote. 

When I connect the system in this way, everything works as expected except that I cannot see video from X1 box on the TV. The receiver’s HDMI Out status light blinks, which I’m told indicates the receiver couldn’t complete the HDMI handshake with the X1. 

Xfinity tech support was not able to help and basically told me the X1 couldn’t function in this configuration and that I’d have to connect the X1 directly to the TV and run a separate cable to the receiver. This works but is not the most convenient configuration. 

When this occurred, one of the first things I tried was changing out my X1 box since it was a couple of years old. I now have an XG2v2-P. I also tried various other changes to the configuration, including changing cables, hdmi inputs on the receiver, and turning off HDMI-CEC and power saving, none of which worked. 

Any other things I can try, or is it true that an X1 video can't pass through an AV receiver, or at least not a Yamaha?