Are you trying to or unlock features (like bridge mode)?

: This feature ensures uninterrupted service during software downloads or upgrades. If an update fails, the device can revert to the stable previous version.

: Contact your service provider directly. Many ISPs "lock" firmware updates to their specific network requirements, and manually flashing generic firmware can cause a loss of internet connectivity. ZTE Support Portal : Registered enterprise customers can access the ZTE Support Software Download page for technical documentation and verified binaries. Identified Firmware Versions