my iPhone 4 I can not activate and when you try to give me a message for activation activation can not now try later

What is the exact wording of the error message?

Is there a sim in the iPhone?

Has the iPhone been jailbroken or modified to work with

other than the original wireless provider?

Did you recently restore the iPhone or update the iOS version?

What cellular provider in which country are you attempting to use

the iPhone with?