Hi kumasama,
With the fear of sounding like a broken record
, the first thing that comes to my mind is to check your router. As other people seem to have mentioned similar problems in other threads, it could be an OBi issue. But for now, let's first check your router.
Since Google Voice does not operate in the same fashion as a standard SIP provider, it is possible that the router is allowing GV traffic but partially disallowing your SIP provider's traffic. If you are able to connect your OBI directly to your internet modem (bypassing the route), that would help quickly determine whether the router is a factor. Also, if your router has a DMZ option, you could try placing the OBI inside that. If either of these options work, then we will simply need to forward the appropriate ports to your OBI.
It seems that Sipgate recommends the forwarding of UDP Ports 5060, 5004, and 3478(if using a STUN server). Here is a link to a FAQ entry that may be helpful with your Sipgate setup:
http://www.sipgate.com/faq/article/415/Problems_making_a_call I believe there is also a higher port range (something like 10,000 to 20,000) that is sometimes recommended for VoIP, but this depends on your particular provider and setup. Try Sipgate's recommendations from the FAQ first, and then report back with an update on your status.
Hope you're making progress,
pc44