Are you installing your firmware and software without the SIM card in? If so, I would leave the SIM card in and have all the software installed during the process. Damage to the phone should not cause problems for connecting to the cellular network. Have you tried leaving the house, going outside, or getting into a different area to try your signal? Maybe your house is a deadzone and the phone is having a hard time picking it up. My room gets like this since I live in Florida where houses are built with cinder blocks to prevent hurricane damage. It really messes with my signal.
I'm in a known good cell location - coverage in my area is fantastic with my provider (Telstra, usually get 5 bar signal on 3G - I do not get LTE on my plan). I test in multiple places - next to my PC, outside the house, down the street, etc. The behaviour I've noticed is that I have no signal regardless of where I go, for about 5 minutes after booting the phone, after which it gets signal, sends/receives any buffered texts, and then fails to communicate successfully after that (i.e., I get the test text I sent myself, then I resend another test, and it fails to send). The iPhone 4 I've been moving my SIM to has been receiving full signal (as expected) at every place I've been testing the HTC One.