Hi richardg51020958 ,
Please provide the exact dot version of the software & OS installed at your system .Also check whether is there any update available for the software after going through "help > check for updates "
Follow this thread to reset the preferences for the Acrobat software :- How to reset Preference settings in Acrobat.
If you are on Windows OS, open Acrobat, navigate to Help menu & repair the installation.
Also check whether is this happening with all documents or with certain one.
Turn off the firewall & antivirus services if they are active.
Check with the different user account as well to replicate the issue.
Let me know if it works.