The bill pay option in the app has been down for at least a couple of months now and it's very frustrating. It's the only reason I even downloaded the app. I'm sorry Xfinity, but you're customer service is only getting worse. And whenever I try to call, I get someone on the line who barely understands me and I can barely understand them. When are you actually going to fix your issues, instead of continuing to make empty promises to your customers?
Here are some other options:
Thanks for posting to the forums @AREllison. Sorry for the experience you've had. I wanted to follow up to see if you were able to able to get your bill paid using any of the other self-help options provided by @RobertWy?
Have you tried uninstalling the app, restarting your phone and reinstalling the app to see if this helps you?