User gets no pop-up in SAP workflow

Hi all,

I have an issue with the pop-up in the workflow. When users get a certain task, a pop-up appears in which they can fill out a user-ID of the person that needs to work on the assignment next.

The issue is that not all users get this pop-up. It appears not to be an issue of authorizations or user parameters.

Also the standard options (Options > Interaction design > Notifications) get no result.

Can it be that it is some sort of setting in Windows or are there more SAP settings I can check?

Thanks in advance.