The app has accuracy issues, especially further in the future. It only receives occasional timetable updates and only when you update the entire app through google play or apple app store.

In short the eurail app cannot be relied upon to be accurate.

In the event that a train you wish to take is not correctly listed on the app on the day you are travelling then you always have the option to add the journey manually.

For reservations it will be the train number and time listed on your reservation that you should rely on.

It is strongly recommended that you don’t activate your pass or travel days in advance, once the day begins (00.01 CET) you then cannot remove that day’s travel if your plans change.

Ok noted, so does it mean that I should book it online for my seats reservations and print it out, then further look in the app when it is nearer to my traveling dates to see if I can find the same one? In the event of me being unable to find the same one, how do I show the person my QR code from mobile pass and the QR code show won't be the same as the one I did my seat reservation on?

Hi Singy. In this case it also applies: they should fine them, it is not smart!

Just wait a little more hrs till anna b fra Sverige comes and links to a long list of ´goodtoknow´ incl on howtodo RES on your own, not via app, cheaper too. F.e. that to go from BE to NL you can also take the hourly BeNeLux trains that do not even need/can be RES. JUst a little slower as the Thalys with high suplmt to pay. Only this €* to/fro LON-can be very hard- and IN FR for the hi-speed TGV you must RES. PLus that these trains also have quota for passholders, far less as the total nr of seats.

So yes, you can RES certainly also via other means, these depend on what train/country and also pass and RES are separate and not interlinked.

Selamat jalan, lah!

Here is the information that @mcadv is referring to. 

Here is some useful information from the experienced travellers in the Community regarding both planning, reservations and activation of pass and travel days. 

 Planning

The rail planner is normally not up to date, as it only is updated once a month, so to be sure of the time table you better check the timetable and availability on the websites of the national railways. The bigger national railways, like DB (Germany) SBB (Switzerland) and ÖBB (Austria) cover several countries. 

 Reservations 

Neither the rail planner app nor the Eurail website is reliable; the app is the most inaccurate. The operator's own timetable is likely to be most accurate.

I usually plan using the DB planner and only add journeys to the app shortly before boarding a train. By that time, the app usually has been updated with the correct timetable.

Just for confirmation - if you acquire a reservation then you can be confident that the time and date are correct and you should be contacted if there is any timetable changes. As the other posts have said the best source of forward timings is the operator’s own timetables as per their website.

BTW, some tips:

Avoid Thalys if travelling between Amsterdam and Brussels (or the other way around). Choose the hourly ordinary IC train. No seat reservations needed, very flexible and only half an hour slower than the Thalys. So no drama if you miss your connection accidentally, just pick a train an hour later.

Thaly’s reservation fee is extortionate. Pass + reservation almost always costs more than most simple advance tickets with Thalys on Brussels-Amsterdam. And the reservations often sell out waaaay in advance.

Alternatives without seat reservations also exist between Brussels and Paris, via Charleroi and Maubeuge (quite slow) or can be done with cheaper seat reservations by going to Lille via regional trains from Belgium and take an ordinary TGV to Paris from there, with much cheaper reservation cost, and a bit of extra travel time.