Huawei p40 lite emergency calls only problem

Gave a Huawei p40 lite which has the problem that display has been replaced in it everything was put back in it in order but now it says that it is only emergency calls.
I have already tried all the tricks, I have run out of ideas so much I know that when I plug the USB connector into the bottom of the phone that is connected to the computer, I choose to transfer data and suddenly I have a network I can make phone calls from the phone to use mobile Internet. then when I unplug the cable there is that there is still a network for a while but then there is that it goes away or until the next power-up it is only usually set only emergency calls,what could it be ,that hardware failure?
me a manke explained something grounding that if i plug in the USB connection then it will shut down earth battery on the phone and it will come back to the mobile network is it possible it can also solve this thing?