I had the same issue and was about to send it back. FM's support is very forthcoming. They provided all necessary UPS stickers and documentation. But just before boxing, I thought I would see if the OW would "power-up" and it did!
WHAT DID I DO TO MAKE IT HAPPEN/WAS IT JUST LUCK??? I do not know but here is what I did.
I left it in the garage overnight in the cold. DID NOT WORK. Then I simply put some weight on the one side of the board tipping it over to the sensor pad side of the OW. I left it like that for 2-3 days while I was waiting for FM Support to come back to me.
I ready to box it up just yesterday when I thought I would try it again. And, it worked.
Armed with the App, I checked the initial voltage which was around 58, and the percentage at 99% when it did not power up. After taking it around the block a few times (2.4 kms or 1.5mi) it is down to 58% at 52.6V.
I did write to FM Support and am curious if the “tipping” over to one side, actually incurred some power usage. Maybe this can avoid unnecessary “recalls” and help others with the same issue.