If it’s still under warranty then yes - simply follow the standard procedure for a warranty return.

Unfortunately that’s how it is with electronic items these days - there is no official way to open these things up and repair them. So the best that you can do is to check in another mains socket, and to substitute in another power cable if you have one - but there is no manufacturer documentation to take you any further.

It’s sad because often it will just be one or two failed components in the power supply - but that’s just how it is now...

You could try generating a diagnostics report and contacting Sonos support. 

Unfortunately if it won’t power up, it won’t be generating any diagnostic data, so all that will tell you is that it’s not currently present in the system? The big constraint at the moment is that the app “upgrade” debacle means that the OP could wait a long, long time to get a response from Support!

Had a power outage yesterday and when it came back on one of my paired One SL’s would not turn on. The are both plugged into the same socket. I am not happy at all. I hardly use the thing. Is this what I should expect from SONOS quality? If they don’t take care of me I will never buy another SONOS product ever!

Hold down power button while plugging in unit. Works.

I suggest that you review or install surge suppression for your electronics.