Activation not possible

Trying to activate my phone I just bought online from Xfinity

When I go to 'xfinitymobile/activate' it prompts me to download an app
When I turn on the phone to download the app, it tells me I need to activate my phone first and prompts me to go to xfinitymobile/activate

So I'm stuck in a loop.
I try to get support help, but the xfinity chat assistant is useless, and I would call (if there was a number to call) but even if I did I can't because I can't activate my phone. So, what do I do???