Hi:
First: I took a look at your attached screenshots. They look perfectly normal and correctly set up. Now, I strongly suggest that you delete that attachment from the forum, since it contains all your personal information (email address and telephone numbers and OBi number).
Based on what you posted, it's uncertain what is causing the problem.
One "Homer Simpson DOH" thing to check would be: does the ringer on your phone work (is it turned off by a switch, or broken)? Check for a switch, and, if you have another telephone, try that phone on your OBi.
Next test: add a check mark next to your AT&T Wireless phone number. Do inbound calls successfully ring that phone when your GV 3740 number is called?