Ever since I purchased the game in July 2018, sometimes the issue, "(Passenger Name) can’t check in!) then I click on it, and the problem is immediately resolved. I’m not sure if this is a bug or something wrong with my building. This has happened with every airport I’ve ever made.
That happens if a passenger wants to check in but can’t line up in the queue. Especially with medium aircraft having >100 passengers, the queue often is too short to serve them all at once.
The problem is solved after the queue moves forward and the passenger can line up.
It has also to do with fine tuning between the system allocating an issue and making a notification, in other words not to ‘panic’ too soon and check if things are really not available/doable. It also happens when PAX are in shops/restaurants behind a shelf/table/chair/etc and cannot directly find a clear path to the gate/chair/toilet/etc. I hope/guess that this will be picked up in Alpa 34.