restore content

Use the controller to force a reindex operation. Under settings. 

Make sure the library is back online and operational  before you do tnat.

Playlists are stored at the speaker level, which generally don’t reset when their is a power outage (ask me how I know!). Where was this music stored? It could be as a simple as a reboot of all the devices at once (not sequentially, they may need to be off all at the same time), including the Sonos, the router, and wherever the music was stored.