My iPad mini (iOS 9.3.3-or lower) needs activation + activation server connection problem

My iPad mini (iOS 9.3.3-or lower) suddenly requires activation after I powered it on and off. I try to connect it to WiFi, but after a few minutes of saying it is being activated, it says that it cannot connect to the activation server. What seems to be the problem? How can I fix it?

I try to use the iTunes button to activate it, but it sends me to the same place that trying to connect to the WiFi goes to, then the iTunes activate button disappears.