Ipad air2: wifi working but no internet connection

hi, i need some help.

my ipad (air 2, under IOS 8.3) connects to the wifi network (which works for other devices, including iphone, and other ipad), but not to internet. The top left of the screen also show connection to 4G.

none of the app is working.

i Have already done a reset of network settings, and a full erase of data and a full restore... But to no result...

Problem was the same in various countries/places this week, location, which means it is the ipad, and not the network/wifi.

any idea?

thank you

would be much appreciated!