Fenix 6s pro wifi issues:
I have a Netgear Orbi AX4200 router/satellite combo. My original fenix 6s pro was able to connect, but it always had issues syncing a Spotify playlist. After a firmware upgrade, my watch was no longer able to see any wifi networks (assuming firmware update related, but who knows). After going through all of the troubleshooting steps with no success in resolving the wifi issue, Garmin sent me a new watch. I am happy to say that this new watch can see all wifi networks in my area and connect with no problem. However, there is still a problem with Spotify syncing.
Spotify syncing:
Although my watch can connect to my wifi again, Spotify playlists take many tries to successfully download. Each time I would start/restart syncing a playlist, the percent complete would get a little bit higher before failing. I am able to sync playlists, but on a playlist of 37 songs, I think it took over 25 restarts to complete. To troubleshoot, I deleted the Netgear Orbi network from my watch, added a basic TP Link router to my network, and added the new router to my watch. Now the watch is able to sync complete playlists without failing and restarting.
I like my Netgear Orbi wifi, but there seems to be compatibility issues with my fenix 6s. If you have a Netgear Orbi router and are having issues with syncing your music playlists, I recommend hooking up a basic secondary router just for your watch.