If it hadn't been working just previously, I would have suggested hooking your OBi directly to the modem for testing.
At this point, I would look around the Callcentric server for your account information again. If you don't find something, such as using the wrong user number or password, I would ask Callcentric for help.
After you get this working, don't forget to block SIP scanners before getting motivated for that at 4AM.