No network/Services

I got a Note 3 Att that works fine but won't read Sim card at first but once it does it won't make orc receive calls. When I enter a number to call then hit send it will show its calling but no ringing then call ends.
I placed the motherboard into another note 3 to see if it was a Antenna issue but still same issue so its in the Motherboard itself. I can only think maybe a software issue...
Anyone know what the issue may be ?