The usual suspect is a missing permission for SMS messages in Google Play -store and/or Google Play Services system settings in your Android device
- Open "Settings" menu from your device and then "Applications" or "Application manager"
- On some Android devices these permissions can be found on "Privacy" -settings (or "Apps & notifications")
- Then open "Permissions" and then look for "SMS messages"
- Give permission to use SMS messages for Google Play -store and Google Play Services - system app
On different manufactures their devices may use other naming policies for their menu items than the ones mentioned above.
If that's the case with your phone or tablet and you're not sure how to gain access or how to grant permissions for SMS messages for these Google Play -store and Google Play System Services apps, then please contact the technical support for your device (device retailer, manufacture or Google tech.support)
Once the SMS verification is passed, you can remove the SMS permissions given to Google Play -store and Google Play Services - system app, for Tracker App installation use SMS verification only once during its installation process.