Not sure what the problem is. You don't even need to activate your pass to be able to book a reservation.

But I wouldn't use the Eurail website to book reservations for Italian day trains. You can also book them on ÖBB for less money (no extra booking fees). Do NOT use the "Seat only” option but add the "Interrail / Eurail” discount to all travellers and then look for normal tickets.

IF you use the other way to REServe-published here many times every day, you save the 2€ fee they charge AND its in most cases independent of pass-so you avoid also this problem (which i cannot explain, but rian is the expert on mobile things). SO; for trains in IT use the bypass to book via Oebb.at=austrain rails, search ticket, NOT just seat, later add discount=your type of pass.

You probably travel further on-so the page will give much more info on how to-it varies an awful lot how difficult it is per country.

But with routes that have trains ev hour or even more, NO, trains will not be all sold out weeks advance-it would make no sense at all to run trains like that

Thank you both. We’re newbies to this whole process. I will book our reservations OBB then. I did notice we had printed seat reservations for our trip Naples to Rome but it wasn’t syncing with the app at all. I just thought it was intuitive in that way and would link them but it appears those two things (global pass and a seat reservation) are independent of one another. That makes sense to me now. I appreciate those tips b/c it is nice to save some money and the headache of this website/app.