Hello 👋🏻
Could be more helpful if you do some test
Plug the charger … color of it ?
Then be VERY careful now
Disconnect power and do not short anything
Then also open bottom lid
Disconnect the battery
Press power for few seconds ( 5/10 )
Re- connect battery
Color of MagSafe again ?
Reset SMC
Color of MagSafe again ?
Press power and see if start …
Yes not …..
Did you replace and check C7771 +- and 1,05 volt to …?
this is a common issue , on this video you get the most brilliant information
https://m.youtube.com/watch?v=pvy-WrDdgYY
Let us know
Ciao 👋🏻