Room only plays when grouped

My Sonos equipment has been working fine for many years.  Over the last several weeks, I have intermittently not been able to play music in my living room (2 Play5 paired speakers), but the rest of my Sonos equipment is working fine.  If I rebooted my wifi, the living room would typically work again...possibly for a day or two or perhaps just hours.  Now the living room will not play, even after rebooting wifi. What I have discovered is that if I group the living room with a room that is already playing, the living room will also play.  If I ungroup, then the living room will stop playing.