Not Showing in App Theory

I believe this is because on your account it is still activated with the old modem when you swap it for a new one at an xfinity store until that old modem you had goes into backlog or whatever they due to reset that old modem you had. At witch your account should then update in the xfinity app with the new modem you have on your account. I hope this makes since and it does take a week or so depending on how fast they erase and reset your old modem. This is my theory. Can anyone confirm? I say this because I had this issue with another type of electronic service.