Which route exactly? as there is no direct train otherwise we can just guess where the problem is.

I’m looking at any route right now. Would just need to get to Hamburg 4/8 or 5/8 but all routes seem to show this message! 

Is there a problem with the website at the moment? What are we advised to do if it says information on this train currently not available?

I have no idea… I have had this problem for several days now :( 

For the trains in Germany you don’t need a reservation, it is only optional. You can book for trains with optional reservation via bahn.com and the seat only option. 

For the trains Paris-Germany you can book at the call center of SNCF for the TGV/ICE Paris Est-Frankfurt and also for the Thalys Paris Nord-Brussel-Cologne. For Thalys you can book also online via B-Europe. There you need a Paper Pass Cover Number. If you have a mobile pass request it via Interrail.eu Social Media Accounts via DM. 

Do you know if it’s possible to use the interrail code on those websites? Like on bahn.com ? :) 

on Bahn.com you just select Seat Only no need to mention your Interrailpass Here a General Overview