The app subscription and purchased phone number - both are associated with your Apple ID on iOS, or Google Account on Android.
- Please make sure that you had and still have an active subscription which is not interrupted in recent times.
- If you subscribed on iOS - please be sure that you have not changed Apple ID - i.e. subscribed through a different Apple ID than the one trying to restore through.
- If you subscribed on Android - please be sure that you have not changed Google Account- i.e. subscribed through a different Google Account than the one trying to restore through.
If these are still true and you are unable to restore your number, please go through the guidelines to get support, raise the issue so we can help you out.