It seems that the System Preferences Security & Privacy -> Privacy -> Accessibility right must be granted to Parallels Desktop in order for many VMs to operate and to access the VM settings panel. During the launch of the application Parallels Desktop a check to ensure that this right is granted should occur. If this check fails then the user should be informed of the requirement to have this setting enabled and brief instructions on where to find it. Then the Parallels Desktop should quit to avoid any confusion. Related to support case #2525752 In my case I unwittingly deactivated this right without knowing the consequences of doing so. This caused caused the application to mysteriously fail, which lead to a support incident and negatively impacted the user's experience with Parallels Desktop.