IMEI not compatible

Does bring your own device really work? I purchased a Galaxy S23 FE phone from Samsung  in Dec 2023 and added it to my Xfinity plan, replacing a Samsung Galaxy 9. It worked OK, but the phone type is still showing as a Galaxy 9 (?). I purchased another Samsung Galaxy S23 FE, again from Samsung and when I tried to add it to XFinity mobile network I got the message, "Unfortunately your device is not compatible". The in-store Xfinity agent was not able to add the phone to the network. XFinity DOES sell the Galaxy S23 FE, so I don't understand why it is not compatible.  I returned the phone to Samsung and I'm awaiting a new one, thinking it was just a problem with the phone itself. In the meantime, I checked my own Galaxy S23 FE (originally purchased through Samsung) that IS working on the Xfinity mobile network and got the message, "Unfortunately your device is not compatible".   So, did XFinity all of a sudden stop the bring your own device program, or is the program a scam? I would have purchased the same phone through XFinity, but the phone is $200 more at Xfinity compared with Samsung.