Fire HDX won't turn on. Indicator shows low battery charge

Hello all,

since my wifes Fire HDX battery was draining really fast I ordered a replacement battery and asked my wife to not charge her device. When she handed it over it wouldn’t turn on anymore, The screen showed a battery symbol with one red bar and turned off after 5 seconds or so.

Well, I went ahead replaced the battery and put it on a charger. I am pretty sure the battery was charged as the charger was warm for several hours and there was a lightning bolt on the battery screen. Unfortunately The HDX did not turn on while charging .

Sad thing is, after charging it still shows just one red bar and no matter what I try it does not turn on. 40 Sec reset, Power + volume up, it doesn’t make a difference. It just cycles through screen off, screen showing the battery status, screen off, …

I already opened it again and checked/replugged all connectors. Everything seems alright. Anyone has some insight or something else I can try?

Cheers

M