Also, in Music Player tab, tried changing to LMS and then changing back to Spotify Connect. It appears that Spotify Connect cannot be restarted this way. Had to reboot to get back to Spotify Connect.
Can play music using LMS with Spotify plugin.
p/s this is not urgent to fix, happy to continue using LMS...
** added
It seems to be a generic error message with many possible solutions
https://spotifyhelp.com/spotify-cant-pla...right-now/
https://community.spotify.com/t5/Desktop...-p/4677307
Tried logging in and out Spotify Connect, but could not access local storage. The 2nd link is installing a ffmpeg compatibility library. Given that ffmpg is used widely, not sure whether it is safe, so did not try it...