My Office 365 calendar won’t load at all on iPad. So I figure I’ll try deleting the app and re-installing. Deleted. Now search in App Store doesn’t work; infinite “loading,” so I can’t find the Calendar app to re-install. Delightful.
If that doesn’t sort itself out. Download it on your iPhone and then it should become available on your iPad… or at least you can go into your account on your iPad and see what you’ve downloaded recently and add it that way maybe.