If you're in France, go to an SNCF ticket office or ticket machine. In Belgium, go to one of the bigger ticket offices. That will also be cheaper. Unfortunately, Deutsche Bahn (who can book many trains) currently cannot book French domestic Interrail reservations.

It should also be possible through SNCF's reservation service by phone:

https://www.sncf.com/en/customer-service/contact-us/telephone

Alternatively, you can try via the app. Go to More > Seat reservation > France > I have a paper pass. Touch Search, then "Book TGV trains with SNCB”. You will need a pass cover number, which you can request via Interrail customer service. This will cost 4 EUR extra per order however (an order can be for multiple persons though). Interrail themselves have an extra fee of 2 EUR/seat and at Belgian or French ticket windows, there shouldn't be any extra fee (not sure about SNCF by telephone).

Okay, thank you very much. I tried with the App and if I pretend to have a paper pass, the train is available, but unfortunatly I booked a mobile pass, so I still can´t book my reservation. (Or can I book it with this pass cover number which I can request from the customer service?)

Is there any other oportunity left or does anyone know, why I can´t book it with the booking service from Interrail?

Currently I am in Germany, so I can´t go to any office :/

I really don´t understand this, it seems like a bug or something.

Anyway, thank you very much for your advice, and If anybody else knows anythin I would be very happy to hear from you!

Kindest regards,

Yes, if you request a pass cover number from customer service, then you should be able to book via the way I explained. But it may be quicker just to call SNCF. SNCF recently removed the online Interrail reservation from their website so it’s their fault that people have difficulties.

En het wordt nog moeilijker!

Als u op zoek bent naar een trein Parijs-Marseille, via interrail, dezelfde dag, kunt u de trein boeken die om 8:11 vertrekt naar Montpellier! Hoe verklaar je dit????

Maar de rechtstreekse trein naar Montpellier is niet mogelijk via interrail

@Nanja

It strikes me that you can book the direct train, departure 8.11, direction Montpellier st Roch, if you do not enter Montpellier as the final station!
Example : Fill in Beziers, Sete, ..., then you can book the train via interrail.

So this could be a solution for you….?

This was a very helpful answer! Thank you so very much! I think it worked know :))

Hi @Sven, we have checked it for you and trains to Montpellier are bookable. The only ones that can't be booked are the connections operated by the Renfe-SNCF Cooperación train because the reservation for that is in paper form and can't be booked last minute. The direct connection with a TGV can be booked in that case. In case it does not show up for you, please contact our Customer Support team directly. Cheers, 

Hm, since normal tickets for the SNCF-RENFE cooperation can be booked as e-tickets (and that has been possible for a number of years now), this really sounds like RENFE/SNCF making life of Interrail passengers more difficult than necessary. And unfortunately, I wouldn't be surprised if they can't be bothered to make it easier.