Nano 33 BLE - can no longer upload code

I have a sketch running on a Nano 33 BLE. Been using it for some time. Made a small change to it, it compiled OK, got about 2/3rd way through programming and 'an error occurred'.

Now I cannot do anything with it. The green power LED comes on, but that is about it. The port menu no longer shows the board. It was COM7.

How do I recover this? Can I recover it, or is it totally screwed?

use double reset to activate the bootloader

Thanks, very helpful.