Have TV Questions? Ask a TV Technician
Welcome. I am Mike, an experienced field technician. We are now connected together on this convenient website where I am able to help you.
Your tv has more than one hdmi port. Plug the hdmi cable into another port on the tv, use the Vizio remote to change the INPUT to that hdmi number. Also reboot the xfinity box by unplugging it's power cord for a minute.
If that does not help then the board inside the tv will need to be replaced. If that is something you would like to attempt, reply back here and I can help you otherwise a repair shop will be needed.
Remember, I will be here with you throughout this entire process. Unless there is something else you can think of, please take a moment to submit at least a 3 star rating at the top of this page before you go. Rating now does not close your question or prevent future replies which are at no additional cost.