cc121 power-on all buttons flash repeatedly?

my cc121 was working fine yesterday.

today when i power on, with external power supply and USB connected, all lights flash repeatedly.

this looks like a diagnostic sign but i can’t find anything in the docs or this forum.

what does it signify please?

OK, I’m guessing it signifies “insufficient power on usb bus”

But the thing is, it should be getting power from the external power supply.

I have tested the power supply on a multi-meter. it’s supplying 12V.

I have tried a different (equivalently rated and polarised) power supply. no joy.

it looks like my unit has suddenly decided not to receive power from an external power supply any more.

could this be some kind of internal fuse blown?

has anyone else experienced this issue?