Digilog is a web app. You don't get it from the App Store or Google Play — you add it to your home screen, and from then on it opens like any other app.
Log in first, and check that the address is go.digilogapp.com before you add it. Add a different page and the icon won't take you into the app next time.
The app used to live at a different address. An icon added before the move still opens the old page — delete it and add the app again.