Mother board does not provide power on battery port to charge it

I have 2 gba sp having the same issue, it is not charger, or battery related, neither fuse F2.

Dunno where to go to, to find out how to repair it.

Symptom : short red/orange light flash when pluggin it on the charger.

Then when controlling the battery port, no power at all or almost nothing 0.0….

I have been changing battery, charger, and swapping with other gba sp that run ok as expected.

Can’t find out.

I have been trying to test transistor on the mother board and could find 2 without continuity, but, comparing with other gba sp working well, it is the same.

I’m lost !

Help !!!!

Thanks a lot