Gost Router/Glitch in the Matrix

I would love for someone to explain this to me. However, explaining what's happening can be as confusing as the situation itself. I don't want to make this a long story, so I'll jump off at, I recently moved into an apartment above my garage that for several years has housed an xfinity black tower modem with an older Netgear router labeled house. In my other apartment I had a newer Netgear router that was wired to the garage router witch is labeled Netgear 29 5G. When I moved into the garage apartment xfinity sent me the new white gateway modem. Because I had the two routers, I just wired them both up. A few months ago after an xfinity service call I figured it was stupid to have two routers so I removed the router labeled house, disconnected, unplugged, no longer in the building. There's only Netgear 29 5G wired to the gateway. But when I wifi connect to that router on my phone or PC, it says, connected with no internet connection. Yet the Netgear house is still an option to connect to, and when I do, with its pass code, it wifi connects and works perfectly on the phone and computer. How can that possibly be happening?