It has already happened to me twice that a Nest Audio suddenly stopped working for no apparent reason. The last time I came back after two weeks' holiday and it simply stopped responding, even though there were no problems before. It seems to be a general Nest Audio problem after all. I looked on the internet to see if I could find a good tip somewhere, but found nothing.
As I have always received a full refund, I have not suffered any financial loss, but it is annoying.

I've had that too, it's simply defective. Best to have it replaced.

The way things are, I wouldn't hesitate for long: Back to digitec, they have always been customer-friendly so far, i.e. replacement immediately or in approx. 2 weeks. Good luck!