First verify your OBi202 is configured as per the following:
http://forum.fongo.com/viewtopic.php?f=15&t=16090The guide is for an OBi100 but the configuration is the same. If you use OBiTALK, you may need to use OBi Expert Configuration.
If it is configured correctly and you still experience the problem, let us know what router you use, or if the OBi202 is connected directly to the internet.