ITS ALIVE!
So I opened it back up, removed the shield and the cart tray and moved the 72 pin connector around. left, right, back, forward a few times, then put a game in and kept moving the connector and testing it, eventually it recognized there was a game! Kept trying more games, all working. So I just put the pieces back 1 by 1 testing after each piece with success!
I dont know exactly what fixed it, maybe the 72 pin connector was not aligned right or maybe the moving it around scraped more dirt off, but it works
Thanks for all the help and suggestions. Im so happy to get this working again, its my original one from when I was a kid so has a bit of sentimental value to me! Its now back as my main console.