An update caused this to break, but it's easy to fix.
Open the Dialing App on your phone that you use to call out, not the Vodia App.
Go to the three dots (burger) on the top right, then Settings, then Other call settings (Calls in case of Pixel), then Calling accounts, then Active calling accounts, and you should see "Vodia Phone" with a switch in front. Turn it on.
Then that's it.
Everything will be fixed moving forward. You'll be able to make outbound calls with the Vodia App.