Here is information about different ways to make reservations for trains between France and Spain.

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105/index2.html?postid=18423#post18423

@Ruben L 

Thx AnnaB!

Thanks, I rang the French number, and despite the really helpful assistant it’s very frustrating to hear that all seats for interrail in France are sold out for the summer months…

Any alternative ideas to get from Barcelona to Turin (11 august)? The agent says they’re sold out, so looking for any tips/alternatives?

Travel via Portbou.

That can't be true. For domestic trains in France, SNCF sell pass holder seats for 20€ until trains are full. For international trains, the number of pass holder seats is limited indeed, although it would still be strange that no international TGV would have any pass holder seats left until the end of August.

The journey Paris-Barcelona was sold out, I would have had to pay a full fare ticket and after I rang again the day after there was indeed the option to get the Barcelona - Turin one. Unfortunately you can only pay via credit card, and not the ones from every country are accepted, which I didn’t know. That’s also a big problem if you don’t live in France. In the endive managed to book a night train vie interrail (only €6 more expensive but worth it considering the problems I was getting for the payment) and we’re doing Barcelona - Turin with regional trains, so no reservations needed. Thanks for the tips, and if I may say, I would just add that payments via the telephone to SNFC can only be done with credit card (French, British, Dutch, Swiss, Luxembourgers and maybe another, but I couldn’t catch them all. Amex is also accepted)