There is a way to factory reset the phones. Based on your other post your Shoretel system would not have the correct firmware for this phone, but it would still operate with the firmware that came with the phone.

Although rare, I have seen a phone or 2 that had some network connection problems. I will assume that you already looks at the other common problems. like the patch cable or network jack. I don't know that a factory reset will resolve this, but it probably could not hurt to try.

I'll send you a PM with instructions.