In which case I cannot do the online Check-in?

Online Check-in is available for all passengers travelling onflights operated by the Alitalia Group* (AZ Alitalia, VE Volare, XM Alitalia Express/CAI First, CT Air One City Liner), with the exception of:

*Minors can only use online Check-in if accompanied by an adult.
**Passengers needing special assistance can request it by calling 06 65640 at least 48 hours before their flight departure time, to ensure they receive assistance according to their specific needs from the time of check-in to boarding.