It is impossible to stop/restart a virtual machine from the Parallels Desktop User Interface because all the buttons are grayed out.
Note: if you run a virtual machine on a Mac with macOS 13, please check the list of known issues first.
If your virtual machine is stuck with a black screen, try performing the steps from KB 123094 first.
For other situations it's required to force quit the virtual machine process using Activity Monitor application:
On your Mac, open the Activity Monitor application from Finder -> Applications -> Utilities and find the following process:
In Parallels Desktop the process name is the virtual machine's name:
Highlight this process, click X at the top left corner and choose the Force Quit option.
- Restart the virtual machine.