Which connection did you originally intend to take? The screenshot you show mentions Milano Porta Garibaldi, which is normally the destination of regional trains. The EC trains go to Milano Centrale.
The message you got also does not indicate that the train is not running. You are only being informed that you need to check the state of the schedule yourself before you travel.
Nevertheless, what you should never, ever, ever do when a railway changes their schedule is cancel your ticket. You have a ticket to Milano for January 4th, so to Milano the railways must transport you. If the railways decided to replace a train with a bus than your train ticket will be accepted in the bus.