Hope you are doing well and sorry for the trouble.
Would you mind sharing the version of the Acrobat DC you are using? To check the version go to Help > About Acrobat and make sure you have the recent version installed. Go to Help > Check for updates and reboot the computer once.
Is this an issue with a particular PDF file or with all the PDFs? Please try with a different PDF file and check. If the file is stored on a shared network/drive please download it to your computer first and then try again.