There is a simple solution to this and once I faced, and finally overcame. Reboot the iPAD. This is the hard reboot, now the poweroff button to conserve battery.
It seems for whatever reason, about once every 6 or 8 weeks, the iPAD has a glitch somewhere with certain internet connections and needs a hard reboot to recover. I have once had to have an individual hard reboot when FaceTime would not work, another, when I couldn't connect to our "guest" WIFI connection at work, and a third time when APPS would not update.