14) I'm trying to check in online, but I'm getting a message saying Check in at the Airport. Why is this?

TUI Flights
This means that online check-in isn't available for your booking. It doesn't happen very often, but it means you'll need to pick up your boarding passes from the TUI bag drop desk when you get to the airport.

The same service is also available for the following airlines: 
Air Europa, Albastar, ASL Airlines France, ASL Airlines Ireland, Evelop Airlines, Germania, Norwegian, Travel Service and Volotea but it means you'll need to pick up your boarding passes from the airline check in desk when you get to the airport.