can’t give up on iFixit. Of course you tried the reset:
Unplug the multi-room interface power pack for a few seconds, then reconnect it. This allows the unit to reset itself after a power surge or power interruption.
and you tried to re-establish a connection:
If NO RESPONSE is continuously displayed, the link between your music center and the multi-room interface may be broken. To re-establish the link, hold the center close to the interface. Press and hold MUTE for about 5 seconds until you hear a second beep. After about 10 seconds, you should hear two beeps to confirm that the link is established.
Note: The music center establishes a link with the closest multi-room interface.
If you have the multiroom interface you could try to control it through a computer interface. Looks like the Bose Lifestyle all use the same serial commands:
Play / Pause....\x61\x45\x43\x43
If nothing, else this should work for you for more troubleshooting. 199402