Both of you: check if there are any available updates for the app and if any options have been set.

But really, you should not use the app to plan, since it doesn't get enough updates to be reliable (latest update 5 weeks ago). National websites and planners are much more up to date and for international planning, the DB website or DB Navigator app is a good choice (2 updates/week).

For Strasbourg - Vienna, there are enough possibilities to travel without mandatory reservations. E.g. set "Appenweier” as a via point.

Thank you for your quick answer ! 
so if i understand correctly it is better to plan our trip not through the "Rail Planner" application, but rather through other sites? how can i know which site to go to? because we want to go to at least 4 different countries.

Yeah I already found a free journey for this one, but my boyfriend can’t find it on his phone and that’s the  problem. We already checked if we entered the  same  options etc… maybe we need to search with an other website

I basically use the DB planner. It has approximately the same coverage as the rail planner app but is much more up to date.

For Italy, www.trenitalia.com. For other countries, Google country + railways and you'll usually find the national railways website, which will have a timetable planner.

I have understood your answers but I don't understand how by going through the websites of the railway companies the routes will be linked to my pass. I would like to know how you did it on your side. Thanks in advance!

They're not. I plan my journeys using other planners because they're more reliable. Then, before boarding a train, I use the app to look up the journey/trains I'm going to use and add them to My Trip and then to My Pass. If a train is not in the planner, then I add it manually.

Thank you very much for taking the time to answer me precisely.