Modem, router or cable problem?

I've had Xfinity for wifi for a few years. With the latest cost increase I decided to try T-Mobile. Was horrible. Lots of buffering, lost signal, etc. Went back to Xfinity but at a lower speed (1000 vs 1200). I contacted Xfinity to activate my modem (Netgear Nighthawk CM2000) and the tech told me everything looked good on his end. I connected my Eero Pro 6e and left the SSID and password that I previously had. My iPad connected and I'm able to stream movies. My phone (Samsung S23 Ultra) is asking for a sign-in. My TVs (I stream) also won't connect. I have a Roku TV, and deleted the network and reset it, but I get an error from Netflix that I'm not connected, even though the TV says I am with an excellent connection. My other TV uses a Google Streamer 4k. It also says I need to login. When I click that message I get a message: The webpage at http://connectivitycheck.gstatic.com/generate_204 could not be loaded because: NET::ERR_CONNECTION_REFUSED.
I've rebooted everything multiple times. Eero tells me my connection is ultra fast. Download 1.27 Gbps, Upload 25 Mbps. The upload light on my Nighthawk modem is solid amber. All cables are tight. Don't know where to go from here. Appreciate any help.