Hello again,
In my case, I cannot confirm the root cause but I managed to fix the issue.
I disassembled the tablet, disconnected the battery. Connected the power supply and I was able to turn on the tablet. This way I confirmed tablet still working.
After, I measured the battery voltages to confirm it was not dead.
Once I confirmed battery was not dead, I reconnected the battery and tried to turn on the tablet and it worked.
I believe this was probably some issue on the power management that was fixed by the hard reset and re-installation of battery.
This may solve the issue for other users, but to open this tablet is a little tricky, you need to gently unclick all the brackets around the screen to remove it. I have posted a video in the forum in the past showing how to disassemble it.
Regards,