Use reputable tools such as the Nokia Care Suite or Infinity Best for legacy devices.
For newer Android-based X7 (8.1) models, a "fixed" ROM may allow for flashing on devices with locked bootloaders or bypass specific rollback protection errors. nokia x7 rom rpkg fixed
If the tool gives an error immediately upon loading, ensure you have edited or removed the tracking lines inside the .mlf file that check for strict hardware versions. Click to let the tool parse the firmware packages. Use reputable tools such as the Nokia Care
Nokia X7 ROM RPKG Fixed: The Ultimate Guide to Unbricking and Flashing nokia x7 rom rpkg fixed