make sure all 3 match in the pjsip_custom_post.conf file.
In the below example I use “gvsip7775551234” replace the digits with your phone number or a random string of numbers, so long as all 3 match and are very unique, so that nobody else would be using the same thing.
client_uri=sip:email@example.com contact_additional_params=obn=gvsip7775551234 username=gvsip7775551234
See what that does for you. If that does not work then the only thing I can guess is that its an issue with the oauth Tokens, you made sure that you generated the tokens for the correct account that has the google voice number right? being logged into more than one account in the top right corner can goof things up if your not careful. (When generating tokens I log out of all accounts and log into only the account I am trying to generate the tokens for.)