Searching/ no service problem (read)

I recently purchased an se from an owner who’s screen was smashed. I fixed the screen (full replace) everything works as it should except searching when I boot the phone and no service if I try to remove the sim.

I’m a majorly expirienced tech so don’t go : pull the sim in and out update carrier settings etc.

I’m thinking it could be one of the ic’S or the antenna. Non of the symptoms for a bad ic appear. I can see the imei modem etc all numbers come up except for the actual network. Field test also doesn’t work.

My thinking is that maybe one of the antenna grounds is loose or something.

How can I test the hardware , I cannot see any problems , I did an Apple diagnostic with Apple and they said the hardware is functioning correctly.

I don’t want to randomly swap ic so if someone could help narrow this down I’d love you forever. Maybe even blow you but you’ll have to take me to dinner first. I’m classy.

Ps no water damage.