There's a new firmware release 7.0.11 for the S1 Pro system
It addresses this issue:
Previously, some S1 Pro Systems would shut down if the AC power was interrupted. On those units firmware 7.0.11 changes the way an interruption to the AC power affects the S1 Pro:
When an interruption in AC power is detected, the S1 Pro will go silent for four to seven seconds. The audio will resume without intervention from you. During the silence, you may notice the channel one LED turn amber. This is normal.
It also contains minor updates for compatibility with the Bose Connect app version 8.1.1 (rolling out over the next week or so).
You can also get the firmware update through the Bose Connect app. If you are already using the Bose Connect app, it will detect that there's an update available and display a download icon on the screen. Tap the icon and follow the prompts on the screen.