Hi Klaas,
Can you try listing this way ?
la –s sap.com_R4_Interfaces -w –u <your nwdi admin username>
Also, as I can see on the sent screenshot you have a very similar other workspace (R4_INTERFACES) and I am wondering whether that caused any trouble. Can you create a dummy activity in any other workspaces to see whether you run into the same problem? You can use dtr webui to create such an activity. Maybe this way we can isolate the problem to see if it is a general one or workspace specific.
Regards
Ervin