Same here. Previously for months buggy maybe 3 times a week with black screen every other day, but starting last week, horizontal white line at top and couple times I got it to work by the "unplug for half hour, install/uninstall" routine. Now nothing works. My workaround is open stream app on iPhone (always seems to work), then cast it to Chromecast. so why did exact same app stop working on Samsung SmarTV.
Same problem here and their poor support from overseas is horrible. I miss the reliable YouTube TV app and will go back when my contract is up in April. The app never works and the interface is a joke for navigation. Xfinity never responds so the only option is to cancel and hit them where it hurts. It is a streaming world with a lot of options.
I wonder if Xfinity is tracking how many times per day I reinstall the app on both of my tvs. It's weird that this problem has been going on for weeks with no resolution.
I just got off the phone with them and they are well aware they are behind the times on the app and it needs and overhaul. I cancelled my service. Hit them where it hurts to force them to fix it.