"Sorry, that didn't go as planned" Error on Xfinity App

I've been trying to get back online for the past day. Last night my internet inexplicably cut out for no obvious reason. My internet setup worked fine until last night.

I'm using a Motorola DOCSIS 3.1 MB8600 router. Several Xfinity app support agents eventually put me in contact with a human being, who was able to get this modem model and MAC address properly added to Comcast's system.

I must emphasize that despite providing my MAC address and modem model to the Xfinity support agents 10+ times, only the Comcast employee who called me (and the only one who had an American accent) did it properly. Please stop outsourcing.

After that Comcast employee helped me out, the lights on my modem now indicate it is receiving a signal from Comcast. The final steps for setup rely on the Xfinity app.

My (current) problem is the Xfinity app is [Edited: Language]. 

1. There are two pages, Overview and Account. Overview is hogged by a 'Your bill is past due' message. My bill is not actually past due. If I follow this page it shows I have $0 owed, and shows my recent payment. Despite owing nothing the 'Your bill is past due' message will not go away.
2. Because of the above message I have no way to initiate activation of this router. I can't make the message go away, even by paying this bill early. Uninstalling the app does nothing. Clearing cache and storage does nothing. Restarting my phone does nothing. The Xfinity app erroneously believes I owe Comcast money so it won't allow me to activate my router user-side. 
3. I can't use the app's magnifying glass icon to search for anything. There is no option to talk to talk to Xfinity's in-app assistant.
4. I frequently receive this "An internet connection is needed to access the app" message on the Xfinity app. Reloading the app via the button it provides does nothing. My phone uses cellular data and can access the internet.
5. If I try to use my web browser, it redirects me to a page requesting I activate my modem. How do I do that? With the Xfinity app that doesn't work!

Going through the https://idm.xfinity.com setup process to try and activate the router doesn't fix my issue. It's a big loop of:

• Logging in with my account credentials,
• Accepting a security SMS,
• Verifying my home address,
• Selecting the address labeled ACTIVE (there is a second account with the same address labeled INACTIVE),
• Receiving an Account Verified message,
• Receiving a Looking for devices on the account message
• ... and then being told to install the Xfinity app, which [Edited: Language] and doesn't work. "I require an internet connection" which I clearly have via cellular data.

It's very clearly a problem with the Xfinity app.