xfinity app login issues

Hello. While visiting our local Xfinity retail outlet, I was encouraged to download and install the xfinity app on my iPhone. The app downloaded without error. Unfortunately, when I enter my xfinity username (which corresponds to my xfinity email address) and password, the app enters an apparently endless loop. The screen display during this loop is the xfinity logo with an envelope and cell phone icon immediately beneath the logo on a dimly illuminated denim blue background. The only activity on the screen is an endlessly rotating "wagon wheel" like progress indicator. I have verified that these same credentials work fine when logging in from my computer in conjunction with the {https://connect.xfinity.com/} site. Repeated attempts to login from the app all end in the scenario described above. Do you have any suggestions? Thank you.