Whoever you're calling with the Google Voice account that has no number, is probably blocking anonymous calls.
I don't think that is the reason, because:
1. None of the numbers work, including toll-free directory assistance (1-800-555-1212).
2. They work fine when I use hangouts to call (but not with OBi202).
I wonder if it could be related to the IP address (I am currently abroad); For OBi202, I am getting a non-US IP address, but with hangout, I am using a VPN to get a US IP address (Hangout doesn't work outside of the US).
If that is the case, why does SP3 (has GV number) but not SP1 work (no GV number)?