You could try using a different charging cable. If this doesn't help, the problem seems to be with the alarm clock. Contact Galaxus directly.

We bought two of them a few months ago and although they apparently still work, I have to admit that getting them up and running was a pain. I remember that the first attempt to charge the battery didn't work but that on the second attempt it was OK (battery problem on start-up?). I've always used the cable supplied with the alarm clock. But I must point out that for two orders placed almost simultaneously, we received one device with a mini-USB connector and the other with a USB-C connector... Go figure?!?

The alarm clock seems to be malfunctioning. I've never had these problems with mine.