This happens if you attempt to upload an incorrect firmware version or a corrupted download file.
The Ultimate Guide to ZTE Router Firmware: Updates, Custom ROMs, and Optimization zte router firmware
If you have downloaded a .bin , .trx , or .img file, follow this process carefully. This happens if you attempt to upload an
To help find the exact firmware or steps for your device, let me know: What is the specific of your ZTE router? or .img file