Question [Q] Replaced screen. Now can't get LTE

Hi there. I replace the screen on my i9505 (The entire screen and digitiser) Everything works fine except for LTE.

It is selected in the options and it is selected in ##4636## as LTE/GSM(auto) however I have not once seen the phone make an LTE connection.

My APN settings are all okay. I have tried 3 roms and am currently running the official stock rom for my network. (I9505XXUGNF6_I95053IEGNF1_I9505XXUGNF6_HOME)

I opened up the phone and checked the the LTE antenna is seated properly and it is.

Can anyone suggest anything else I could check/try?

Thank you