One speaker in a pair stopped working - can't resolve

Pair of symphonik, worked fine.  One speaker power got unplugged for a week or so, plugged it back in, now only left speaker works.  Diagnostics show the pair is active and both speakers are connected with strong signal.  Tried to unpair, but the android app would not let me.  Figured I would try the windows app.  Windows app required an upgrade.  Meanwhile Sonos radio is streaming out of the left speaker only during all of this.  Windows app starts upgrading and lo and behold both speakers are working in proper stereo!  Upgrade taking a couple of minutes and finally says COMPLETE….at which time, the right speaker dropped out again and I am back to where I started.  What is going on here and how do I fix it?