Xfi app shows wrong modem so I can't fix wi-fi problems

I have 2 modems in the house (both are provided by Xfinity). One runs the voice line and ties directly into the wall jacks. The other is a new Xfi modem and controls my internet and wi-fi. When I log into the Xfi app, only my voice modem shows up. I am having numerous wi-fi issues, but I can't see devices or check/change any settings because I can't get to the modem in the app...I tried to use the online automated system, as well, but when I tried to do anything, it kept trying to "fix" the voice modem.