Time ti reservation

You should not activate your pass OR any travel day until just before travelling. You never know an illness or any other unforeseen problem thwarts your travel plans.

Once a travel day has started, it’s impossible to get them back. Luckily, you can de-activate both your pass and travel days before the start of the validity period or the travel day or the pass.

A lot of people got into trouble already with this.

Anyway, answering your question:

Registering your journey in the app =/= reserving a seat on a train.

There are three categories of trains in Europe

• Trains with mandatory reservations, mostly long distance international traffic or high speed trains like Eurostar, Thalys, TGV, Frecce trains, AVE,…. You’ll need a valid ticket (=your pass) + seat reservation in order to travel on these.
• Trains with optional reservations, almost all German/Austrian/Swiss trains  (ICE, IC, Railjet, EC,...). Reservation is not necessary to travel on these, but recommended on busy times, small group or if you want specific seats.
• Trains with free seating, all the rest of the trains in Europe (most trains).

Please find all reservation details in the topic below, please read it attentively:

Paris Zürich on TGV Lyria has expensive, even extortionate, seat reservations. You can avoid these by going to Mulhouse/Bellegarde/Strasbourg (Fr) and take a regional train to Switzerland. Details in the topic mentioned above.

Btw, not entirely sure. But as you are a French resident, I think for your inbound/outbound journey you get your reservations for free. You can find them at the Guichets in the nearest station in France.