One of the default security on Android devices is not allowing users to install apps from outside the Play Store.
But due to unfair sanctions and bycodes by Google in relation to some countries and people, we could not put the Rojt application on Play Store, but it’s fairly easy to install apps from unknown sources on Android.
Note: if the above steps don’t work, go to “Settings → Biometrics and security (or Privacy) → Install unknown apps.” Enable the toggle for Rojat com app.