Can't Upgrade OP-1 to OS version 218

I’m hitting a strange problem that I haven’t seen mentioned here.

I’m currently running OS version 14203 on my OP-1. I downloaded version 218 and tried to upgrade through the normal process: hold down COM, turn on the OP-1, hit 1. The OP-1 connects to my Mac, I drag the OS firmware to the drive and eject the drive. But when I then hit COM to kick off the install, nothing happens. It’s been awhile since I last upgraded the firmware, but I always remember it giving some almost immediate feedback when it kicks off the update. My OP-1 sits there indefinitely and doesn’t appear to do a thing. I let it go for about an hour with no feedback and no progress.

My OP-1 otherwise seems to be working okay. It was sitting unused for a couple months, but I gave it an overnight charge a couple days ago and have been using it.

Any ideas?

Thanks in advance,