iPhone 5c has no imei number, no liquid damage

I have an iPhone 5c that requires repair.

At first it had a signal problem, I checked the network and settings and found it has no imei, I've encountered this before and in my experience found that a clean in the ultrasonic and then a reflow or clean works.

In this case it has no signs of liquid damage but I gave it an ultrasonic clean anyways,,

Have tried

-resetting network settings

-gave it a chemical clean

-tried another battery

Is there anything else I can try? Any chips or ICs I should be looking at and checking?

Thank you