In order to be able to view the digital class register and make entries, you need the authorization "View class register". 

You can check whether your profile has this authorization as follows:

Click on the menu at the top right (three dashes) and then on "Account & Settings".
Call up your profile by clicking on your name.
Under "Authorizations" you can see which authorizations your profile has been given.

If the authorization "View class register" is not activated for you, please contact the Sdui contact person at your school.