Network Help (Ubiquiti Access Points)

Hi all. I'm having some problems with my home network and could use some help. Sorry for text wall, but I'm not a network guy and will try to provide as much detail as I can.

Spectrum is our service provider and we've got their1 gig internet plan. A couple of weeks ago, my wife was having problems connecting to WiFi on her work computer. She spoke with her IT department and their conclusion was that it was an ISP issue. We called Spectrum and a tech came out and determined that our router needed to be replaced to accommodate the 1 gig plan, but she didn't think that was causing the connectivity issue. FWIW, we reset the old router/modem right before the router was replaced, and my wife was able to connect. In any case, the Spectrum tech replaced the router because we were only getting like 400mbps and we pay for a gig. The new router upped our speeds significantly.

Our network includes the Spectrum router and modem in a central tech closet. We have three Ubiquiti U6 lite access points throughout the house/garage, and a Linksys router in our outside area which acts a relay/extender. The access points are POE and the linksys router is hardwired with CAT6. Prior to the tech replacing the router, we had no connectivity issues except for my wife's computer, and everything was functioning as it should. WiFi signal was very strong throughout the house and in our outside area.

After the router was replaced, the access points were still connected to the original network. In other words, if you pulled up the wifi network access settings on a device, it would show both the old network (XXX-01), and the new network (XXX-44). You could connect to either, but the old network didn't provide internet connectivity. We also noticed that the farther reaches of the house were not getting internet connection, so I figured it had something to do with the access points.

After speaking with the IT guy that installed the network, I reset the Ubiquiti access points to try to get them to forget the old (XXX-01) network and adopt the new (XXX-44) network. Now, I'm unable to connect to any of the access points. All three of them show up on the app and indicate that they're "ready for setup," but when I try to connect to them to get them to adopt the network, I get the "Cannot Reach AP" message. I've tried to reset them all numerous times.

The linksys router relays the connection outside fine, but for some reason, these access points have stopped working. It may be a long shot, but does anybody with network experience have any ideas? I'm at my wits end here and need to get this resolved, because half my house's smart features aren't functioning because of the lack of connectivity. Ubiquiti was no help, FWIW.

Thanks in advance.