Hi Knut,
Did you try the steps my colleagues and I listed above? If so, what were the results?
Do you see Docentric in your toolbar at all or is it just greyed out? If Docentric is available in the toolbar, does the document you are working on have a DDSP file uploaded?
I would also suggest going through this forum post, trying the steps described there, and letting us know if the issue persists: Docentric Word Add-on Disabled? Here’s Your Step-by-Step Solution