Hello Berndm,
We apologize for the inconvenience caused, as per the description above, you are not able to convert the PDF to Word, Is that correct?
The record shows that you are subscribed to Adobe ExportPDF service on your current Adobe ID, you can access the service through the URL https://cloud.acrobat.com/exportpdf with your Adobe ID and password on a browser like Chrome, or Firefox, or Safari.
If you are using freeware Adobe Reader DC and getting the error message, please sign out and sign back in Adobe Reader DC using your current Adobe ID, check for updates from help>check for updates, reboot the machine after the installation of updates and try exporting the PDF file.
For more troubleshooting, you may refer to Troubleshooting Create PDF, Export PDF, Adobe Send, Fill & Sign … services(PDFPack or Document Cloud Services).
Feel free to update this discussion for any further assistance.
Regards,Anand Sri.