No display after removing screen and replacing battery/charge port?

Hi all

I have an old tab s2 that wasn't charging and the screen was cracked. I removed the front screen and then the back cover and replaced the charge port and battery. All connected up but then the display was flashing colours. So I bought a new screen but now I get no display at all.

I'm thinking the LCD flex cable is damaged as the part that goes into the display has separated? It's like a black sponge part that was glued down and is now separated.

I have ordered a new cable in the hope it fixes the problem. Does this sound like that's what's wrong with it?

Thanks