The Interrail system will need to verify your mobile Pass at least once every 3 days, to ensure its validity and prevent fraud. Therefore, you'll need to open your App (it does not update itself in the background) at least once every 3 days when you're connected to the internet. 24 hours before your 3 days without internet, the App will send you a reminder.
In case you don't open your App with an internet connection for more than 3 days, your mPass will be considered inactive. This means that your pass cannot be used offline any more, and you'll be able to use your pass again only when you'll be re-connected to the internet with the open App. Please note that it can take a couple of minutes to re-activate your Pass in our system, so keep your app open for some time after reconnecting again for the first time.
Some trains in Europe (especially high-speed trains) offer a Wi-Fi internet connection to the passengers. It may be useful to check if this option is available while travelling.
Don't forget to keep the notifications activated in the Discover EU Travel App to be reminded when you need to connect to the App (one internet connection every 72 hours).