You need internet (via any means, e.g. 4G, wifi etc.):

1. to activate the pass
2. to activate a travel day
3. to generate the barcode (tapping on “Show ticket” for the first time on a travel day)
4. at least once every 72 hours.

#1 is only needed once; #3 is best done immediately after #2. After #3, you don't need internet anymore on that day and you can still add additional trains to your pass and show the barcode. Turn on flight mode if it takes too long.

Thank you very much for your help.  A couple more questions.  If I am going to take several trains one day to my destination, can I generate all the tickets first thing in the morning to use them during the day even if I don't have a connection when I have to use them?  And one more question.  If I make a seat reservation, do I have to print it and then what time to present is just the reservation or the interrail ticket as well?  Thanks.

You get for every travel day a new QR-Code. This means, you can take all trains that you can get that day (from midnight to midnight CET - central European time, the scheduled departure time will count, if the train arrives the next day it counts only 1 day). BUT: don’t forget to add every train to the app (this works also offline). 

Your Ticket is the Interrail Pass QR-Code, the reservations are needed only for some trains that require a reservation or if it optional. You have to show both ticket and if needed for the train the reservation.

You can add all your planned trains to your trip at any time after loading the pass into your app. (Think of your trip in the app as your diary, and like all diaries you can add or subtract entries at will. Until they are moved to your pass they are just entries in a diary and are not valid tickets.

So if you plan to travel on several trains in a travel day all you need to do to transfer them to your pass on the day by flipping the button showing in your trip.

If you have flipped the tab and then circumstances mean you do not travel on that train you simply disable the tab and the train will be removed from your pass.

(Note if you have activated a travel day and then don’t travel on any train that day you cannot cancel it after 2359 the previous day).

This is why we advise users not to activate the travel day by adding your first train of the day until you are sure you are travelling.

Extra trains can be added to your trip at any time before boarding and then added to your pass, so your pass is totally flexible.

Thank you Angelo.

Thank you Yorkie.