T-Embed stuck in bootloader - it thinks it's a Feather

[SimonA]

I'm not very experienced with these boards, and I was trying to upload a sketch to the T-Embed using PlatformIO. I had used a different (wrong) S3 version (the adafruit feather S3) in the platformio.ini file. It got part way through uploading before erroring and now when I plug the board in, it just registers as a USB drive called FTHRS3BOOT.

I've tried using bossac to install the firmware from a built pio version using the right board - get an error saying no device is connected on the COM port

I've tried using the firmware flash tool suggested in the firmware readme file of the T-Embed github repo - it all seems to be setup the same as the picture in the readme, but clicking start does nothing

I've also tried installing circuitpython using a downloaded .uf2 file and the circuit python install tool - it copies over the file, the drive disconnects, reconnects and it's still FTHRS3BOOT and nothing has changed
(the install tool complains that it expects a file that isn't there after the initial installation)

Is there anything else I can try to effectively 'factory reset' this board? or have I bricked it?

Any help is much appreciated