Why ZTE phone doesn't connect to a mobile operator after its last update?

[AC Question]

After doing a security update on a ZTE device (Z667T), it wouldn't connect to a network operator.. How can i solve this, please..? i have done factory reset but it won't still connect to a mobile operator..

 

[B. Diddy]

Welcome to Android Central! Go to Settings>Mobile Networks>Network Operators​. Does your carrier appear there? If not, contact your carrier and see if you need a replacement SIM card.