Facing the same issue since yesterday :/
Did you unplug the Beam, then hold the join button, then plug power back in to reset?
Check out this video:
Hi @Nick722851 and @Homesystem011992, welcome to the Sonos Community!
A lone flashing white LED can mean two things; either the speaker is connecting to your network or it is trying to boot up. I’d suggest temporarily wiring the Beam Gen 2 to your network to see if that helps, if not, then the Beam may be experiencing a boot failure.
If you’ve followed the steps in our Factory Reset support article or the steps in the video @Pools-3015 had linked, then the best next step would to be submit a diagnostics after attempting the factory reset and to reach out to our support team. They have the necessary tools to look into your system and can help you with troubleshooting the Beam. If a replacement needs to be done with the speaker then they can also discuss the options you have.
I hope this helps!