I can see and book the 18.32 Verona - Turin on 23 Aug on raileurope desktop site for passholder,

Hi! Thank you for the reply, unfortunately I tried again and it always gives me no train. I tried it both from my PC and from my phone. can you explain to me where I'm wrong?

I see the connection too. Maybe clear your browser cache, use a version in another language or use another browser or computer? Buy these rail europe reservations on desktop, not mobile.

If it still doesn’t work, you can also get Italian reservations via ÖBB, see this guide:

You can also take regional trains, without seat reservation for this connection (taking longer, with a change in Milan of course). Plenty of alternatives :)

I also read the guide you mentioned above which was very useful for me to get the sleeper tickets for the OBB NJ night Milan Vienna. I also made seat reservations on Vienna Prague on OBB. I took that same morning from desktop and not from mobile place for all the other trains. On OBB it gives me the regional trains that change in Milan which obviously don't require a reservation, so they are also free. I cleared the cache, tried from desktop and then from mobile with the desktop version, and changed the language. I'll try with another phone and if not I'll go to the ticket office as soon as I've purchased the Global pass.
If you say you can book I don't see why I shouldn't be able to.
Thanks for the info

Weird indeed, anyway. It’s still far away in railway terms, I wouldn’t worry too much about this train: plenty of connections possible for this route.

Trenitalia is a bit slow in uploading it’s schedules, I would try again in a couple of weeks.

Hi, I'm coming back to say that I managed to see from the raileurope.com website.

 thanks to BrendanDB for suggestions!
I cleared the cache, restarted the computer, opened the site, removed the Italian citizen and added a European citizen, left the English language without a translator and did the search again: finally all the trains, both the regional ones and the Frecciarossa, were visible. I can also select the seats but it asks me for the globalpass number which I don't have at the moment. I know that I can put a fictitious one so in the next few days I will calmly get these last tickets for the return.
I wrote it here in case it might help someone.
have a good day everyone 

 thanks to BrendanDB for suggestions!

That’s really weird that you had to do all that to get the website to work!

Maybe worth reporting it to Rail Europe (if you can be bothered).

Glad you were able to get the reservations!

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I had a problem just yesterday, trying to make TGV reservations. It kept showing me availability, but then failed during the booking process. Eventually I realised it couldn’t find the exact seat type I requested, but instead of telling me that, it just failed.

Hi, I'm not very surprised, generally "Italian" things are more complicated. Furthermore, the very fact of being Italian does not make it easier for me to buy the Frecciarossa ticket, as if I were cheating, rather than returning home as permitted by the global pass. Partly for the same reason why you can't buy seats on the Frecciarossa website because unfortunately many of my compatriots tend not to be very honest. In fact, I think it made a difference to say that I was a European citizen instead of an Italian one. But maybe I'm wrong.