piraterick Hi there!
Let's start with a few basics:
- Have you installed Sandboxed Google Play? (That includes all 3 apps - GSF, Play Services and Play Store)
- Did you install the app after installing Sandboxed Google Play?
- Do the 3 Google apps as well as the Google Duo app have the network permission enabled?
If the answer to all 3 of the above is yes, can you try granting play services the Phone and SMS permissions and try again?
If you're still facing issues, please let me know.