need more info -- how did the battery go flat? did you keep the unit plugged up via usb or did you let it sit unused for a while and the battery went flat on its own?
whats your method for charging it? via a computer or wall plug?? did you try another usb cable and/or charging source (different power brick,shore power, etc...?)?
The unit died because I was using it in the battery ran out of charge.
I use the USB-C cable that came with it on an iPhone brick that is a 20 W. I use a 65 W laptop charger that didn’t work then I used a 65 W wall charger and that didn’t work. I tried to reset the battery while it was plugged into the 65 W charger and that didn’t work either.