I upgraded to Spotify Premium for my kids . . . and now when I try and play Spotify Connect on the streamer (172xs running latest firmware) it's saying 'Error incompatible Spotify version'.
Assuming you can play your new account other than on the naim connect stream - eg using your Spotify app directly on iOS or Android device. Then, I f you've ever connected to a different Spotify account on your 172xs, including a free trial afaik, I think the only way to clear out your old credentials and log into the new ones is to do a factory reset on your streamer. There's an issue with security keys that get used by the naim firmware to enable the connect streaming to work. If this works for you, we should close the loop with the software team to add a "reset Spotify connect" function to the app menu.