Hope you are doing well and sorry for the trouble. As described you are unable to export the PDF to Word.
Would you mind sharing the version of the Adobe Acrobat DC you are using? To check the version of the application go to Help > About Acrobat and make sure you have the latest version 21.05.20058 installed. Go to Help . Check for Updates and reboot the computer
Is this a behavior with a particular PDF file or with all the PDFs? Please try with a different PDF file and check.