My MacBook Pro not starting up changed new batteries still not turning on . But charging cable show green light

Resetting SMC could solve the problem.

How to reset the System Management Controller (SMC) on your Mac - Apple Support

I have this same issue. Apple support and many others say the same thing on every site to reset the SMC. Apple doesn't really have an answer for this issue, just like every other issue with MacBooks. This does not work at all. It's either an adapter issue or motherboard issue, depending on how old the macbook is. Mine was a motherboard issue.

Hope this helps.