µMoth Hardware Flash update fail (Mac OS 14.6)

I have 2 AudioMoths an AudioMoth Dev and a µMoth both of which I bought recently. Whilst attempting to commission both devices I have successfully configured and updated the AudioMoth Dev to 1.7.0 having been prompted to do so by the AM_config app.

The same process did not work for the µMoth, the AM-Flash app started the update but stopped half way through at the bootloader(?) stage (light blue bar part way across)? I have not been able to get any of the AM software to recognise the µMoth since. The USB cables are the same in each instance; the AM Dev appears in the Mac hardware report under the USB 3.0 hub but the µMoth does not. Rebooting the Mac has no effect.

I have looked through many posts here old and more recent but nothing I try connects the µMoth to the Mac. There is 3.0V available from the µMoth auxiliary connections and the switch on µMoth has continuity when operated in all three settings. No LEDs light up now at any time. The AM software does not become enabled (because the MAC is not showing the µMoth as being connected?) Attempting the 'Manual Instructions to Switch to Flash mode' in the Flash app using the paper clip has no effect, the Current Status says 'No Audio Moth found'. Any advice on how to recover an otherwise brand new µMoth would be much appreciated.

(The Mac is an Intel model - not a new M1. The µSD card is formatted Ex-FAT but I don't think that's relevant as it is not populated to update the firmware. I have tried connecting to the AM Flash app with the µMoth switch in both the Off and Config positions.) Many thanks,Steve