Unable to reserve seat on some trains

Book here:

Deutsche Bahn: bahn.de - Verbindungen - Ihre Anfrage

4,50 € per person 2nd class / 5,90 € 1st class.

@Hektor Isn't the reservation also optional?

It is optional. But I understood that @Revolver wanted to do a reservation. 

Yes, but I just wanted to ask to be sure for my knowledge🌞

Hi. Thanks for your replies.  Yes, we want seat reservations but the main problem is that it’s telling us that our Interrail passes aren’t valid on those trains.

The advice from the experienced travellers is to neither use the Rail Planner to make the planning nor to make the reservations.

The time tables in the planner is only updated about once a month so the data there is not reliable. 

The advice from the experienced travellers in the community is to use other ways to make reservations than the Interrail/Eurail website. You can look at the guide in the link:

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

If you, after having looked at the guide, have questions about how to make specific reservation, please give your travel details (departure date, time and route) preferably in a new topic, and you will get advice. 

I you have a global pass and you’re not having a problem with your residency, it’s valid (in general). I think the app’s message is not because of this (so there might be any other problem with your pass). 

It's not only that. You also pay an extra fee of 2 EUR per ticket and person in addition to the seat reservation fee when you make the reservation through Interrail.

Thanks for the additional info.  I didn’t realise that booking direct would be cheaper.

Because of that we have made a Post (The link is in the Answer of Anna B. at the top. ) 

Yup, and Interrail already use an expensive provider to begin with, that charges 6€ per person and train. That makes 8€ in total per person and train, whereas DB does it for €4.5/5.9 per person and journey.