Can't log in to Xfinity App to manage devices

Error Message: Let's Try That Again: We had some trouble accessing your account. Please try again. If you've already tried troubleshooting and still have an issue, we can help. Chat with us (Xfinity Assistant link)

The AI assistant is entirely unhelpful regarding the issue. I can log in to my web account, but device access is only in the app.

I have tried all troubleshooting tips (cleared cookies and cache, reinstalled app, rebooted router and phone, changed password, and so on).

Would not recommend this company.