HTC One X Unlocked, Not recognize any Network

My HTC One X dual sim , open back removable battery, sim, ext ROM card, European edition , Unlocked will not recognize ANY GSM network. It recognizes the inserted sim card, phone number on card, network the card belongs to . But it will not link with any network, has no signal, can not make phone calls. Every thing else work, including wifi. The “status” page states that the “Mobile network state ” is unknown, the the “network” is unknown, the phone number is stated.
Under “search for network” page it comes up with “error while searching for network”
What do I need to do to make this phone pickup signals to make phone calls.?
Can you help me please ?