Touch screen not working after screen replacement

I just put a brand new screen on a samsung a55. When I turned it back on the lcd works perfectly but the touch doesnt register anything. I have disconnected and reconnected all flex cables and still the same issue. I took the main flex cable out of my samsung a35 and tried the screen again on the a55 but still touch doesnt work.

So I connected the a35 board with its power/volume cable taped on to the new screen (as board doesnt sit in 55's frame) keeping the a55's battery, sub board and main flex cable. And the screen works perfectly.

So it must be something on the a55 main board which is causing the touch not to work. The fact connector looks perfect(I cleaned with Isopropyl alcohol just incase)

The a55 touch was working before the original screen got broken. But now its not.

Ive repaired quite a few phone before but I have never had an issue like this before.

Any advice would be highly appreciated.