Facetime Activation. Could not sign in. Please check your network connection and try again. How can I fix this?

[iMore Question]

"Facetime Activation. Could not sign in. Please check your network connection and try again."

The only threads I could find relate to iOS 7 but I'm running iOS 8.4.1. I've tried network reset. The router is running fine, and I'm able to access the internet. What do I do next?

 

[SwitchBeach]

Re: "Facetime Activation. Could not sign in. Please check your network connection and try again."

What country?
What carrier?
What carrier was/is the device originally from?