Forerunner 165 Music wifi sync issue stuck at 9%

I'm setting up my brand new Garmin Forerunner 165 Music. Wifi connects ok, but music sync with apps such as Spotify always get stuck at 9% synchronisation. I've tried a watch restart, hard reset, limited wifi settings to 2.4GHz, using phone hotspot for wifi - none of which help.

I have also have an old Forerunner 245 Music that syncs fine on the same wifi network.
Can anyone offer other suggestions please?