Other apps send a notification when there are changes made in the app, to tell the users to upgrade the app. I have a Samsung (I don't know if it matters), but there is no "update-button", so when Zenler has done an update I have to uninstall the app and then install it to make the new functions work. There should be a notification in the app, and possibility to update the app easily. I can't ask my student to uninstall the app and log in again.