I currently don't see any prices on the Interrail website:

Maybe that's a temporary issue. Trenitalia shows prices but their website does not sell pass reservations anymore.

There are a few things you should be aware of though:

• Trenitalia seem to have sent incomplete data and therefore the interrail reservations module shows this train as a connection with a change in Messina. On their own website, it's a through train.
• Possibly, because this connection is shown as 2 trains with a change, the reservation module would let you pay a reservation twice.
• There are no seats on this train, only couchettes and sleepers.
• You can currently only book complete compartments in Italian night trains. This is still COVID measure. Nobody knows when this will change.
• Interrail has not implemented in its reservation module the possibility to book one complete compartment for 2 (or more) people. When you want to book for 2 people, Interrail proposes 2 complete compartments, so that's expensive.
• Often, the regular fares for night trains available via Trenitalia are lower than the pass reservations. Currently, for 2 people, this train is available for €115.80 in total ("Super economy” fare). That's a couchette compartment for 2 people, without using a travel day. With more people, the price per person drops even further.

Thanks for the response. I booked it now through Trenitalia. It is the best solution. Greetings, Eva