With which company did you make the reservation?

You will have to ask them, or look at the conditions that come with your reservation.

Thank you! I made the reservation through the Interrail website, but the train company is SNCF. Now I look at my ticket, I see there’s a number I can call. Wish I spoke French… but I’ll give that a go.

If you have reserved your ticket via Interrail, you must cancel your reservation here.

According to the information I find on the interrail website, you can find the conditions for canceling your reservation in your reservation overview.

The only way to do is:

Cancel via the source you booked @-this will incur a fee. DK how much. With the current backlog in anything not-ultra-urgent, it also probably will take quite some time before money is refunded.

Then book (assuming there is still an empty comprt available) the 4-people comprt

Preferabl via another source, as this app charges extra p.p.

That FR nr also has an option (or should give it in the intro-tune) for /en/-this may take a longer wait.

I want to book a sleeper reservation for Paris-Tolouse on May 28 and potentially back Tolouse-Paris June 7. I don't see reservations open for this train on the interrail reservation service. There's only a suggestion for a bus on the 28th. This is on the official SCNF website as well. Does it mean it's just booked up on these days already? 

Nvm I have found the answer to this. 

4-berth couchettes in France are 1st class. If you want to use them, you also need to pay the difference between 1st and 2nd class fares.