Water damage - new screens don’t work, only the original LCD turns on.

Long story short, bought a phone then found out it had water damage. The original screen will turn on and display the lock screen, but touch does not work. I sourced a few replacement screens and …they all light up black. The phone still boots, but no display shows. The original screen still displays though. I know the replacement screens are not the problem. Any ideas?

I have:

Cleaned the connections with alcohol

Disconnected cameras, speakers, et cetera

Heated up the phone a bit with a heat gun

Am I just screwed? I’m taking it to my buddy’s shop Tuesday so he can try.