It’s hard to know for certain if Google Voice outbound messaging is down, as the service can encounter issues due to a variety of factors. That said, there are some steps you can take to try and diagnose the problem.
First, if the issue is only affecting your account, double check all of your respective settings and make sure everything is correctly configured.
Second, you may want to check the Google Voice service status page by visiting the following link: https://www.google.com/appsstatus#hl=en&v=status. This page will list known issues and indicate whether Google Voice Outbound Messaging is currently experiencing any issues.
Third, if the issue is more widespread, it’s a good idea to search online to see if there are any other users discussing a similar issue. If so, you may be able to find a workaround or a solution.
Finally, if you’ve been unable to diagnose the issue on your own, it’s best to reach out to Google directly. They have an extensive Support Center that you can accesshere: https://support.google.com/voice/ . A representative can help you diagnose the issue and find a suitable solution.