Hi @Dsugar.
Welcome, thank you for reaching out to Sonos Community since you already tried some troubleshooting steps let me try to assist you.
Once you turn off any Sonos speakers it needs some time to reconnect again to your wifi connection, have you tried at least 3-5min to see if the speaker will show up again or not?
If the speaker is showing a flashing green light after powering up, you'll need to add it back to your system.
Also if possible to hardwire one of the speaker directly to the router for the speaker to get a better signal or so called SonosNet
If you need help with any other information, please be sure to let us know.