reservations

You dont have to book the reservations through the interrail website. There are also other places that sell the reservations. What routes are you having trouble with and when are you planning to travel? (maybe you are just to early?) 

This guide lists some of the sites and how tot book seat reservations on them: https://www.seat61.com/interrail-and-eurail-reservations.htm . For more detailed tips please mention the route and date.

Thank you for your reply. I plan to leave Poland for Berlin, then Munich, from Munich to Italy, and then from Italy to Austria. I want to start my trip on April 12.  

The mandatory Reservations for most italian IC and Highspeed trains can be best booked from ÖBB (Austrian railway) you just have to select Interrail under Discounts. (they dont charge a booking fee on top of the reservation cost).

Thank you very much for your help. I have one more question. Is it possible that if it says there are no available reservations, these seats will still become available before April 12? 

Please mention route, date and departure time for any reservation you don't manage to book. There are multiple possible reasons why a reservation doesn't work and without details it's impossible to say much more.

It's about trains in Italy. I can't make a reservation for them. 

Everything except the Intercity notte should be reservable from ÖBB. Just select Interrail under Discounts when searching for the journey to purchase just the reservation.

Thank you very much for the information. If it says that the ticket is unavailable, does that mean I will no longer be able to make a reservation, or will they be available later? 

which one of the of the 4 jouneys is the problem?

Atleast the first train you posted seems reservable on the ÖBB website.

Also you cab take the NJ295 all the way to Rome (would save you the additional reservation (13€) for the FR. No connection to miss but a bit slower.

For the Intercity Notte you could try raileurope.com (they charge a 2€ reservation fee on top of the cost of the reservation just like the interrail reservation system)

There is a weird quirk with the Intercity Notte, and depending on what accommodation you want, you might need to use a different site. 

From Seat 61: https://www.seat61.com/interrail-and-eurail-reservations.htm#Italy

- Rail Europe can reserve sleepers but not couchettes

- Italiarail can’t book single sleepers, but can book everything else

- Interrail won’t let you book sleepers with a second class pass, even though you’re entitled to,  and often won’t even tell you what type of accommodation you’re booking

That can mean multiple things. One of them is that you used the incorrect method to book.

Add the Interrail/Eurail discount and do NOT check "Seat reservation only”.