Browser cache or old config corruption. Fix: Clear browser cache. Perform a hardware reset (30-30-30 method: hold reset for 30 seconds while powered, unplug power while holding for 30 seconds, plug back in while still holding for 30 seconds – rare but effective).
: If the update is for security patches, your ISP is obligated to push it to your device remotely. Troubleshooting Zte F600w Firmware Update
Save the .bin or .config file to a secure folder on your computer. Step 4: How to Install the ZTE F600W Firmware Update Browser cache or old config corruption