Your Sonos product was not found

I have 3 Sonos Play5 and they all used to work. Suddenly, one stopped working, for no obvious reason. When I try to reconnect it, I get an exclamation point and a message that my Sonos product is not found and asking me to move it closer to the router. The speaker is right next to the router, while my 2 others are much farther away. What gives? I tried a Hard reset with no success