“Could not activate iPad”

This is an iPad we have been using for years. Then today it shut itself off and came back on needing to be activated. It is connected to WiFi but keeps showing this screen saying “your iPad could not be activated because the activation server is temporarily unavailable. Try connecting your iPad to iTunes to activate it, or try again in a couple of minutes” every time it tried to activate. What should we do? How do we connect it to iTunes..? Of course we have already turned it on and off a few times. Thanks