The trip in your online account is not synchronised with the app, except for the activation date.
As to getting a valid ticket, did you follow the steps described on the page below?
https://www.interrail.eu/en/interrail-passes/interrail-mobile-pass/getting-started
If you have added journeys to your pass and then tap on "Show ticket”, make sure you select the date for which you have added a journey. You can do that at the top of the screen.
Additionally, it is not a good idea to activate a pass in advance, because you never know what will happen. If something unexpected happens on the planned start date and you want to change your start date, then it it too late: you can only cancel activation until 23:59 CET on the day before the validity starts. So once you've tested the pass, the best is to deactivate it and only activate it on your start day.