No Service

[Darkstar Industries]

I have just received a Nexus 4 off ebay today. Said it was a month old, unlocked etc.
I got it for the Mrs. She powered it up, and inserted her O2 sim and it said "no service". I then tried my Three sim, still the same.
We haven't done a thing to the phone but turn it on. Is there a reason for this?
I've attached the software details.

Going into the network settings, set automatically doesn't seem to do anything. And when she clicks mobile networks, which usually shows a list, nothing happens.
The IMEI is present in the phone and I've checked that it isn't blacklisted, it's not.
So far I've tried different modems, tried going from 4.3 to 4.2 factory image, still no signal.
Tried CM, no signal. Nothing I try brings the signal up. Is this a lost cause?

 

[N4Newbie]

If you haven't done so already, try it this way:

Hold power button until menu pops up. Select the option to power off the phone.
After phone shuts down, remove SIM tray and insert new SIM (or just reinsert old one.
Hold power button until you feel the haptic "bump" and release. Phone will reboot.
Still No Service?

The point? I learned that this phone will not recognize a SIM card until the phone has booted / rebooted. If the phone's OS is already running when you insert a SIM, it will not read the SIM until the next bootup.

 

[Darkstar Industries]

I just tried that again to be sure, still nothing.
Obviously, the guy I bought it off swears blind it worked before he shipped it and mentioned that maybe and antenna became detached on transit...
I really don't want to return the phone, but I'm running out of options.