If your current carrier firmware hasn't disabled the "Local Upgrade" button, this is the safest route. Connect your PC to the router using an Ethernet cable. Open your web browser and go to 192.168.0.1 or 192.168.8.1 .
Wait for the update process to complete. This may take several minutes, depending on the size of the firmware update file and the device's performance. zte mc801a firmware flash link
The flash corrupted or a factory reset is needed. Re-flash the device using a different, verified firmware version and ensure you wipe the previous user data partition. If your current carrier firmware hasn't disabled the
Flashing third-party or unapproved stock firmware voids your manufacturer warranty. zte mc801a firmware flash link