Hi
I am having the exact same problem! I have tried everything.
I have tried the exact same settings I use on my iPhone 5, and on my ipads (1.gen, 3.gen AND 4. gen) but only on my new iPad Air - no syncing! My calendar doesnt even appear in the calendar as an option to show (or not). Same issue trying to add my wifes gmail calendar - also working neatly on all of the above mentioned devices!
I am using the m.google.com server (setup as exchange)- as I don't want all of my wife's multiple collegue-shared calendar-reminders. But this is the setting that works for me everywhere else!
If I use the pre-set google-mail/calendar option (not exchange) I am apple to get my calendar in calendar-app. Though this do work for my on my account - I won't use it for my wife's (because I cant seem to turn off all of her collegues reminders (though I can turn of showing their calendars...))
Hope someone can shead some light on this matter!