Mozzila VPN on Android sometimes appear to automatically turn itself off. The explaination could be in your settings on Android: Go to settings, - select Apps, - - choose Mozzilla VPN in the list, - - - go to Battery and select background Use, go back to Mozzilla VPN in the list, - - - go to Mobile Data, - - - - turn On "Allow Background Data Usage" - - - - turn On "Allow App while Data saver is On" now your VPN shouldn't turn off any longer. When restarting your phone the explaination why the Mozilla VPN is OFF is that to keep your security, the app requires re-authenticating with their servers (new encryption key).