Try to repair installation (For Windows Only) Go to Help > Repair Installation. and check if that helps
Are the files located locally on your computer or is it on a shared network drive, try downloading the files to your computer and check . If its on a shared network please add the file and folder path to Acrobat. Go to Edit (Windows), Adobe Acrobat/Reader (Mac) > Preferences > Enhanced Security > Add file and Add Folder Path > Click OK and Check.
For testing purpose, please try to turn off the protected view Go to Edit (Windows), Adobe Acrobat/Reader (Mac) > Preferences > Enhanced Security > Turn Off the Protected View and Uncheck the Enhanced Security > Click OK > Restart the application and check.
Note: Please turn on the security after testing irrespective of the result.