3DS no power, no charge!

Hi all, I really need some help with a broken 3DS. I bought it on eBay as broken/parts but it seems to have an issue I have never seen before.

So when it arrived it doesn’t power on at all when you press the power button nothing happens no orange light no blue light nothing at all. I opened up the 3DS to have a look to see if there was any very obvious issues and there didn’t seem to be corrosion, broken pieces and water marks are intact.

So I’ve purchased a new battery, new charger and also a set of ribbon cables for the right button because I broke it opening. I’ve confirmed the voltage of the battery is fine and the charger also works for my other console. The ribbon cable replaced really easily but I don’t believe that would have any effect but it’s still not working?

I plug it into the charger not nothing happens on the DS, no lights, nothing! I’ve left it charging for an hour and again nothing happens! I’ve tried multiple batteries and cables. I just don’t know what else to check or look for?