"Error loading application resources. A resource file is either missing or has been corrupted. The application will now exit." 

If you receive the above error when launching LockDown Browser for Mac, it typically indicates that the LockDown Browser install is corrupted. In most cases, it indicates that necessary configuration files are missing.  These files typically can be found at this location:

/Library/Application Support/Respondus LockDown Browser/config

If that file location is empty, or missing the "id.txt" file, this can be the cause of the error. A reinstall of LockDown Browser should resolve the problem.