TRMNL Bricked. Cannot flash prior firmware. Help.

Like others, my TRMNL was bricked by the OTA update. Tried following the instructions [here ](https://usetrmnl.com/flash)to flash to 1.5.12 but the firmware won't install. I keep getting the following: "Failed to initialize. Try resetting your device or holding the BOOT button while clicking INSTALL."

Tried that many times but it's not working. Any suggestions?