Regular tickets for that train are on sale, so I think reservations should be available.

There’s some good advice here for TGVs from Belgium to France

Hi @MaartenBrusseleers I have the exact same problem. German, Swiss, or Swedish train operators have an option to make seat reservation for interrail pass holders. SNCF seems to be lacking behind. I also tried calling, but I had the same problem, I was on the line for 10 minutes with no answer. They say they have strikes, that might be one reason. I have the same situation than you, a TGV that is bookable through SCNF Connect is not through Interrail website. From my experience, SNCF does not facilitate things when it comes to international train connections, they have been removing very good connections and making it more difficult to navigate France from other countries. I was surprised to learn they don’t have an option for interrail booking given that other similar train operators in other countries do so. In other words, the service they give is not good.

You can try to do as I did: change your booking date to for example March or April and see if the booking is available - that was the case for me. If yes, maybe in some months you will be able to book, although I can’t be sure.

Since you seem to live in Belgium, the best is to go to a ticket office where they sell international reservations. That will also be without any booking fees. These TGVs from Brussels are quite popular and pass reservations sell out quickly so don't wait.

Another possibility is to call SNCF. Press #85 for English, no booking fees, reservations are sent via email. You can also call Belgian railways but their phone number is quite expensive to call.

@ralderton thank you but this information wasn’t very useful. I’ve tried all that already

@Xavi Thanks, I can’t book for earlier dates so I assume it has to be booked more than 90 days beforehand effectively

@rvdborgt *sigh*, I was fearing that going to Brussels to book in person was going to the only option.

So far for getting a bit cheaper tickets than booking directly. This website and the system to book (to go to France anyway) are truly terrible. The worst customer service and experience I’ve had in a long time. I hope seats are still available since I might not even be eligible for the 85% refund on my pass. Booking a plane would have been cheaper and faster. So far for trying to go green by train.

It doesn't need to be Brussels:

https://www.b-europe.com/NL/Veelgestelde-Vragen/Tickets#InternationalStations

Aarlen, Antwerpen-Berchem, Antwerpen-Centraal, Bergen, Brugge, Brussel-Centraal, Brussel-Luxemburg, Brussel-Noord, Brussel-Zuid, Brussels Airport-Zaventem, Charleroi-Centraal, Eupen, Gent-Sint-Pieters, Hasselt, Kortrijk, Leuven, Luik-Guillemins, Mechelen, Namen, Oostende, Ottignies.

@MaartenBrusseleers you are right. The train needs to be part of the solution to climate change but train operators and governments make it so difficult for us customers to book, or afford, or find routes.

If you are interested in learning why this happens, this short video explains it very well: https://www.youtube.com/watch?v=kY7vjbPb-SI

Here’s more information from Investigate Europe’s in-depth articles on the topic of European railways:

https://www.youtube.com/watch?v=hRFtFelZcVE

https://www.investigate-europe.eu/en/2021/derailed-europe-railway/

Thanks for the quick info guys. I’ll give Leuven or Brussels Airport a try.

@ralderton sorry if I was a little blunt, I’m just very frustrated with these booking problems.

Don't worry. Yes, it can be really frustrating sometimes. 

It’s crazy that you can find and buy a flight to any airport in the world in 30 seconds, but booking a train trip to the next country needs a PhD and three weeks of research.