I have been following the "Get started with the dev board" page and am currently flashing my Coral for the first time using a mac as my host computer.
My screen terminal shows "request [####] was not queued to eplin-bulk," and my fastboot terminal show errors with clearing the input and output pipes, and is currently Rebooting into bootloader. It's been stuck like this for over 30 mins.
For reference, I used (Installing ADB on macOS) instructions to download fastboot, and (https://coral.withgoogle.com/docs/dev-board/get-started/) instructions for every other part of setup.
This is the output from the fastboot terminal:
Sending 'bootloader0' (1006 KB) OKAY [ 0.048s]
Writing 'bootloader0' OKAY [ 0.190s]
Finished. Total time: 0.264s
Rebooting into bootloader OKAY [ 0.024s]
Finished. Total time: 0.024s
Sending 'gpt' (33 KB) OKAY [ 0.018s]
Writing 'gpt' OKAY [ 0.309s]
Finished. Total time: 0.346s
ERROR: could not clear input pipe; result e00002ed, ignoring...
ERROR: could not clear output pipe; result e0004051, ignoring....
Rebooting into bootloader
Fixed the issue, but not entirely sure what it was that did it. I went back through the instructions I linked in the question, redownloaded the system image, and the flashing process was successful