First of all, make sure that the router has been placed properly. Avoid setting it up at a place with too many electric appliances. If you still find, Xfinity Wi-Fi router not working. Here are some steps to fix the error.

Steps to fix Xfinity router not working:

 Check the Ethernet cable and all the wires and cables attached to the router. The wires should not be twisted or corrupted. Plug them correctly.

 You can visit the official page of the Optimum network and see if there is some maintenance breakdown. You will be notified about the same of the website.

 Try changing the channel on your router.

 Restart the router and perform the power cycle. Unplug the devices and wait for a few minutes to plug them back again.

 Check for latest updates and update the firmware of the router.

 Reset the router back to factory default settings.

 Check your router properly for any physical damages.