There is a problem with Adobe Acrobat/Reader. If it is running, please exit and try again (523:523)

 Try opening Reader then go to Edit/preferences/ security(enhanced) uncheck enable protect mode at startup.

1. Go to Edit > Preferences > General.
2. In the Application Startup panel, check or uncheck Enable Protected Mode at startup.
3. When the dialog appears asking if you would like to continue, choose Yes. This preference sets:

[HKEY_CURRENT_USER\Software\Adobe\Acrobat Reader\10.0\Privileged]
"bProtectedMode"=(0 = off; 1 = on)

1. Choose whether or not you would like to have a log file created.
2. Restart the application.

Protected Mode preference

https://community.adobe.com/t5/acrobat-reader/there-is-a-problem-with-adobe-acrobat-reader-if-it-is-running-please-exit-and-try-again-523-523/td-p/9442057?page=1