Folks .. I've just spent almost a week sorting out my Sonos system and resolving issues. Some of this info might help someone. Especially if you don't have time to read 100's of articles online. Ironic I know!
I initially had S1 and S2 setups.
S1 - 2 x Play 5's as a stereo pair
S2 - Playbar + Gen 1 Sub + 2 x Play:1's
Issue 1 - never managed to connect both Play1's as rear surrounds
Playlists not able to share between S1 & S2
Fed up with latest S2 app .. appalling!
Decided to downgrade everything to S1
Tip 1: Sonos says to reset every speaker BUT instructions say to hold join button until flashing red & white etc
Went round in circles until one time when I held it longer until I got green flashing lights .. then it worked as expected.
Tip2: (Should maybe be Tip 1)
Keep your S2 app so you can downgrade to S1 .. (same holding join button much longer trick also helped with this.)
Tip3: Gave up with using Rear surrounds so now using Play1's as a stereo pair in the main TV Room group.
Tip4: most homes have a wifi range extender in use .. and Sonos doesn't like them. Advice is to have at least one Home Theatre device connected by ethernet cable.
Hope some of these help you!