Not charging at all, what is broken?!?

Can someone help us diagnose it because soo far we had tried multiple different chargers, opening the back plate, checking for damage (found blue rust on the solder of one chip, it seems to have been bridging contacts and it was most likely from vinegar fumes (white alcohol vinegar spill that evaporated), so then we cleaned the surface corrosion off carefully with a dry new toothbrush, there seems to be none remaining on the surface), unplugged and re-plugged the internal battery, used the little reset button on the inside, held the power button down for a while basically all of the easier things we could think of, tried powering on while plugged in but with no battery..... but soo far we still have only one idea on what it may be and its the seemingly resolved issue of the corroded chip, unless it caused further damage.

How can we diagnose it further? Maybe check if that chip still works? So far the only thing still left to do for us is try to fully disassemble the laptop and check under the board to look for any more corrosion or any other damage, but on the top of the board there's nothing suspicious that we noticed. Maybe get some tools like a multimeter or some tool and check what works or not (We don't know how to tho).

What tools do you think we need to diagnose and fix it (most likely)?

What should we look for to try and fix, as far as common damage or easily fixable stuff goes, to not waste money on extra equipment or spare parts if possible?

We are looking for advice in general but any knowledge is welcome, thank you

PS: can send photos and provide further detail if you can help