Beats Flex won't charge or reset

I've had my Beats Flex for a fortnight.

In that time I have charged them daily. Twice they failed to charge and I had to reset them to make them charge.

Now they will no longer charge at all. I have confirmed that the cable, PSU and wall socket work.

The advice is to reset them: If they have no power, you can only do this if they are plugged in afaict.

However this does not work any more.

When I press and hold the power button and vol down, I get a rapidly blinking red light immediately, then when I release, the light goes white then red then switches off. They do not charge.