The most dangerous outcome of a failed firmware flash is "bricking" your device. If the unlock-zlt-p21.bin file is intended for a slightly different hardware revision, or if the upload process is interrupted (e.g., due to a power outage or unstable connection), the router’s bootloader may become corrupted. Once bricked, the device will not power on or function, rendering it useless.
Look for System , Maintenance , or Software Upgrade . unlock-zlt-p21.bin download
Visit the official manufacturer website to see if there are official, global firmware updates that support broader network compatibility. The most dangerous outcome of a failed firmware