I got some assistance from Obihai support. This actually worked, except that the phone doesn't take ring or accept incoming calls. Here is what they said:
"You need to create the equivalent
gmail.com on the same Google Voice account. This will be the way to configure it to the OBi device. Google forces you to create
gmail.com to have it usable with Gmail (MY ACTUAL EMAIL ADDRESS) call phone. So, please do the following:
-Login to your
google.com/voice with the email MY ACTUAL EMAIL ADDRESS
-Upper right, click on the 9 dotted icon,
-Click the "gmail" or "email",
-Proceed with creating a new gmail account under the same Google Voice (MY ACTUAL EMAIL ADDRESS) account.
Once this is done, you can configure that new gmail account into your OBi."