If the phone still shows "Invalid SIM" after the unlock, check if the APN settings for your new carrier need to be entered manually.
Change your USB port (use a Rear port if on a Desktop) or try a different USB cable. zte z320 unlock nck dongle link
The specific software application installed on your PC. Step-by-Step Guide to Unlock ZTE Z320 with NCK Dongle If the phone still shows "Invalid SIM" after
If the phone enters "Field Test Mode," the NCK software can usually still communicate with it to perform the unlock. zte z320 unlock nck dongle link