No HTML Editor in Service Manager Client

I am working with SM9.30 using the SM Client RTE Version: 9.30.281. If I try to create a new knowledge document via Knowledge Management >> Contribute Knowledge I do not have an HTML editor to create the content. The reference tab of the form is just empty. The behavior is the same for all available document types.

Any help/advice/idea will be very apreciated.

Thanks, Norbert