SteveInWA is right. This doesn't work. GV won't give you two sessions right up front. Which is what is causing the symptoms you're seeing. The Obi is forwarding your call, so it won't ring, but GV doesn't have a line to connect it, so it goes to the great bit bucket in the sky.
You'll need to add another SIP carrier.
So, once you have a carrier on SP2, you'd dial the star code you want (for always, for busy, or for no-answer) and then: **218005551212# and that should work. After that, you can make changes in the UI if needed. Or just use the star codes.
Fun Fact: If you get an initially free voip carrier, like Callcentric, you can make non-PSTN voip calls for free. If you use SIP Broker to route the call, you can code that in your call forwarding. For example, I just tested using
voip.ms to call a Callcentric line, by coding this in the CallForwardUnconditionalNumber field: SP2(**275*46217779999999)
**275 is the route to SIP Broker from
voip.ms (also from Callcentric and several others.)
*462 is the carrier code to Callcentric
17779999999 is the format of a Callcentric account number.
So, what happened here is a call came in to GV on SP1, it was sent to call forward via
voip.ms on SP2 to SIP Broker who routed it directly to a Callcentric account number without going through another DID.
I see a couple of different carrier codes for Sonetel in the carrier directory on
sipbroker.com. You'd need to test them to see if any work. Or call Sonetel's tech support for guidance.