The timetable that the Eurail app presents is often unreliable, particularly if you are looking far in advance.

Use other sources such as trenitalia for Italy or DB, OEBB for most of Europe whose planners are much more accurate.

If a train you want to take is not in the app on the day of departure then you can make a manual entry to add it to the pass.

Keep in mind that .italo trains on this route are not part of Eurail. Only trains of Trenitalia (local: R and RV and long distance (reservation compulsory) IC and Frecciarossa.)

As previous posts say the IR planner is routinely slow in adding future timetables and in my experience it is particularly poor at adding Trenitalia Freccia and IC services until a few weeks before. Although you cannot book reservations via the Trenitalia website it is an excellent source of future train timetables, and then you have to be patient for those trains to loaded before making reservations. Personally I have always been able to reserve on Italian trains in the few weeks before departure, and never been on a totally full train as on the main routes they have regular services and plenty of capacity.

Again: most from faraway over the oceans are extremely worried monthes advance about ´full ´ trains-just to reassure you, this is complete nonsense-it only applies to a very few select crack trains, notable this €* to LON. All major lines in IT have several trains/hr-very much like the VicRail or StateRail locals-this is not the 1/month Ghan. For global planning-how long it takes, how often etc simply use a samedayofweek the upcoming week and re-check a week or 2-3 before travel. THere is/was an age-old rule that bookings are only possible from 2 MO advance-only here+there is is now a little longer

What date are you looking at?