No service, Emergency calls only.

As the title says No service, Emergency calls only.

The IMEI is recognised, and I've tried changing the preferred network type. No luck.

The signal strength is always at minus.

I opened it up thinking there was a physical problem and discovered that the antenna connection on the PCB in the bottom right corner of the phone had come off so I got a new board and replaced it, along with the antenna for good measure, but still nothing.

I'm at a loss now and really don't want to give up on it as I've just replaced the screen.

Any help is greatly appreciated.

Thanks in advance,

David