The Italian summer timetable has not been published yet or at least hasn't been uploaded into Eurail

I don't think the 19th August train is sold out, it simply isn't available to book at the moment

When it becomes available book on tickets.oebb.at (no booking fee, add Eurail as a discount and select one-way tickets).

In general it's best to avoid booking on eurail.com because they add 2€ booking fee per person per train. See advice :

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

https://www.seat61.com/interrail-and-eurail-reservations.htm

@thibcabe thanks for that info. I’m completely new to Europe travel and this is my first time taking a train in Europe.

Follow up questions:

1. Can I use Eurail discount without a global pass or buying any kind of discount pass?
2. The site you mentioned (oebb.at) seems like an Austrian site. How are we able to book trains within Switzerland and Italy using an Austrian transport provider?

Thank you so much!

You can use it with any Eurail/Interrail pass (or combination of passes) that covers your entire journey.

Many European railways companies sell tickets and reservations for journeys to/in other countries, so that's nothing special. ÖBB however is the only one that offers pass reservations for Italy online. It's entirely legitimate.