Can't download the app for Xfinity Mobile

Xfinity sent me a new SIM card for my iPhone 8.    I added the card and went to the "setup" directions, which direct me to a message that I need to update my software. 
When I go to download the app, it says my iPhone 8 is not supported. 

Also, this is the exact same phone I used 2 years ago with Xfinity mobile, so I don't understand the issue.

HELP!