Obihai support team is still looking into this issue. In the mean time, please try the following in your OBiTALK account:
Click your OBi number 510xxxxxx (300XXXXXX, 200XXXXXX, 500XXXXXX, 630XXXXXX, 610XXXXXX, 600XXXXXX).
At SP1, delete your Google Voice account.
Click SP1 again, follow steps to re-authenticate back to your Google Voice account.
When "Connected", please make test calls in/out.
If status "Backing off..." remain, then click the OBi Expert Configuration blue button at bottom / Enter OBi Expert blue button.
Modify the DNSServer1 parameter value: Select System Management / Network Settings / to DNSServer1 / input 4.2.2.2 (or 8.8.8.8 ).
Click Submit to save and your OBi device will reboot automatically.
Allow up to 1 minute to complete, check your Google Voice status for "Connected" then make test calls.
Please stay tuned and we will do a follow-up.
Thank you and best regards,
Obihai Technology, Inc