Online, it's only possible via the Interrail reservation service, with an extra fee.

Via DB, you have to go to the ticket office, a DB travel agent or call DB (collection via DB ticket machine possible). DB does not sell the reservations for the ICE/TGV Germany - France online.

Hello, 

I am commenting this post because I have the same problem, but for a Stuttgart-Paris travel. And it doesn't seem to work via the Interrail reservation service either. 

It says :

No price results were found for this connection. It is possible that the train is fully booked for pass holders. Please try searching for another connection or find an alternative way to book.

When this appears, is it sure that it is fully booked for pass holders? Do I still have a chance if I go to the info desk in the train station?

The train I'm trying to book is for today, departure time from Stuttgart 10:52AM and arrival time Paris 2:05PM.

I'm afraid the quota for pass holders is full. This often happens with these trains a few days in advance.

I don't understand, since I was able to add the journey to my pass, I am a ticket holder. There is enough space in the train so that I have a ticket, but not a seat? It's not logical... I have a ticket, but I can't take this train?

Can they give me a seat that is not in the quota for pass holders? I mean if the train is not full, it would be nonsense to refuse to book them to pass holders. 

To reach Paris, you can search for a reservation-free connection to Strasbourg (should be possible every hour) and then a TGV to Paris. DB still cannot book Interrail reservations for domestic trains in France trains, but the Interrail reservation service (2 EUR extra fee per seat) should be able to book them. Alternatively, you can use the Belgian railways website (4 EUR extra fee per order, you need a pass cover number) or call Belgian railways (no extra fee, but there are phone charges, no pass cover number needed, delivery via email).

But I can't book TGV either... Also Paris is not my final destination, I am going to Le Havre. And even for Paris-Le Havre I can't. For all the trains that I check, it tells me the same message. 

Then please check the Belgian railways link.

On the Belgian railway link I can't enter any German train station ("no matches for your search query", I tried with a couple of different stations), + I don't have a pass cover number. And I tried to call the phone number, but it says that it is temporarily unavailable (or maybe it's my phone that blocks the number that are not free).

I'm also trying to call the DB reservation service (+49 30 2970) but I have been waiting for more than 50 minutes now... 

It seems like the whole world is against me

Please read what I wrote. Summary:

1. DB cannot book domestic Interrail reservations for France.
2. Online booking of reservations for TGV/ICE Germany - France is only possible via the Interrail reservation service but your train looks full. DB can also book these (ticket office / DB agent or via phone) but of course not when it is full.
3. Domestic reservations for France can be booked via the Belgian railways website or phone service (the phone service can book much more, but not always deliver as a PDF). The Interrail reservation service should also be able to do this.

For specific booking problems, please always mention on this forum the exact train (date & time) you're trying to book. "It doesn't work” is very difficult to troubleshoot...

Thank you for your help ! I managed to take the trains that I wanted, but not in the way that I was supposed to, regarding seat reservation. I am going to explain, maybe it could help others who struggle with the seat reservation or if the train looks full.

Here is the itinerary (wednesday december 15th, 2021) :

8:27 Munich - 10:45 Stuttgart : Train ICE 690 (no seat reservation required)
10:52 Stuttgart - 14:05 Paris Est : Train ICE 9574 (seat reservation required)
15:40 Paris St Lazare - Le Havre : Train TER 3119 (seat reservation required)

I was struggling to book seats for Stuttgart-Paris and Paris-Le Havre via the Interrrail reservation service. It would always show me this message (not only for these 2 trains, but also for other ones) :
“No price results were found for this connection. It is possible that the train is fully booked for pass holders. Please try searching for another connection or find an alternative way to book.”

At Munich train station, a DB agent at the ticket office told me that the quota for pass holders seemed full for the Stuttgart-Paris train. He checked other possibilities to go to Paris but they also looked full. He told me to go to Stuttgart and ask to the DB agents at the ticket office. But I couldn’t, since I only had 7 minutes connection (I was supposed to take another Munich-Stuttgart train earlier, to have more connection time, but it got cancelled ).

I tried other booking ways as suggested here, but none worked. On the Belgian railway website I couldn't enter any German train station ("no matches for your search query", I tried with a couple of different stations). And I tried to call the phone number, but it was temporarily unavailable (or maybe it's my phone that blocks the number that are not free). I also tried to call the DB reservation service (+49 30 2970) but I waited for 2 hours and noone answered.

When I was in the Munich-Stuttgart train I asked for help to DB agents. They both told me to board the Stuttgart-Paris train without a seat reservation, and to go straight to the agents after boarding. They were pretty sure that the agents would be able to book the seat for me while I would already be on the train. As I had a ticket and was only missing the seat, they thought it would be ok and that I would not have to pay a lot for the seat reservation.

So, that’s what I did. Once on board, I was able to book my seat with the DB agent. He said that it’s not usually something they do, but I said that it was his colleagues’ recommandations. He accepted but he made me pay 33€ So it didn’t really go like his colleagues had told me, but I was ok with it since it was surely my fault (if I had booked my seat early enough, I probably wouldn’t have had these problems).

Once in Paris, I still had to try to book my seat for the Paris-Le Havre train. At the train station, before boarding the train, I went to the SNCF agents who were working on this specific train (I mean, not the agents at the ticket office). They told me that I didn’t have to book a seat for this train ! If I understood well, the system is changing and the seat reservation (at least for Interrail pass holders) is not yet required, although this appears on the Interrail app. So they let me board the train with only my ticket and no seat reservation. What a relief for me !

I’m sorry for this really long post but I wanted to give some tips when facing seat reservation problems. In short :

• When a train looks full or no reservation service works : ask the agents at the ticket office if they can still book a seat for you even if the quota for pass holders is full. If the train is not full, there is no reason not to open the remaining seats. Otherwise, board the train and try to book your seat directly with the agents onboard. This is risky, but if you absolutely need to take this train and are ready to pay more than expected, you can try. It worked for me but I can’t guarantee it works every time, I guess it depends if the agent decides to be nice or not. Also it worked for me with Deutsche-Bahn, I don’t know if it would work with another company.
• About the trains in Normandie, France (with the brand “NOMAD”, departures from Paris St Lazare) : the seat reservation is not required, whereas it is usually indicated on the app. Apparently it is about to change, but for the moment the seat reservation is not mandatory. So if you take one of these trains, check with the SNCF agents if the reservation is really required (I recommend to ask directly to the agents working on the platforms, not at the ticket office).

It was my first time as a Interrail pass user. Now I know that the seat reservations must be done the earliest possible But in case of booking problems, I hope that my experience can help others !

Moderator note: to tap into your comment about the NOMAD train in Normandy, seat reservations on these trains are now mandatory. 

As to the ICE reservation to Paris: as I said, the only way to book online is via Interrail. The 33 EUR onboard fare  (almost the triple normal reservation fee) is the normal procedure if you board without a reservation.

As to the NOMAD trains: as far as I know, there was a temporary COVID-related requirement to have a reservation but this was lifted quite some months ago. @Nanja, I think this should be checked with SNCF and corrected in the app.

Thanks for flagging rvdborgt. I have passed it on to our product team for a check with SNCF and corrections to made accordingly. 

Update: We've checked it with SNCF and received the following update, @rvdborgt: The Normandy region has changed its inventory and reservations are now mandatory.