The message that I should check my Internet connection is the most annoying thing about this game, to me anyway.
In all the times I’ve had that message only one time was it actually a problem with a connection to the Internet, the satellite link used to connect Tarawa to the outside world was down. (TSKL, the worst telecommunications company on the planet.)
So, no, it’s not that my tablet is in flight mode, or that I’m not connected to wireless, or that the router I’m connected to is not connected to the Internet; it’s that your servers are down. And at least on a tablet you should be able to test for all of those conditions and show a more accurate and useful error message.