Some of our Xfinity customers have seen "No Signal" on the TV when they configure the Pass-through option. In this case, the HDMI cable from Xfinity is plugged into the ONSCREEN HDMI In port and the ONSCREEN HDMI Out port is connected to the TV. After rebooting, the TV shows the Xfinity programs fine, but when a call comes over ONSCREEN the TV shows "No Signal" when going back to Xfinity.
This is a problem with the TV syncing back to the Xfinity signal. It should clear up if you follow the instructions from Xfinity to set the display resolution of the Xfinity cable box to 1080p instead of Highest Available.
Adjust your video display using the X1 On-Screen Guide
Learn how to manually configure your video display using the Xfinity X1 On-Screen Guide.
Note: Your X1 TV Box will automatically configure to the highest video resolution possible for your TV at setup. If you want to manually change your video display settings after setting up X1, follow the steps below.
Video display
To access Device Settings:
Press the xfinity button on your remote.
Scroll over to Settings (the gear icon) and select it.
Highlight Device Settings and select it.
Then, navigate to Video Display and select it.
Select Video Output Resolution. On this screen, choose your desired resolution and press OK.
Once done, you can also toggle Zoom between Full and None.
Press Exit to return.