Symptoms

Parallels Desktop cannot be started. The notification window Unable to start Parallels services appears.

Cause

Parallels Desktop cannot connect to one of the required services.

Or

The absence of the restricted flag on /Library/StagedExtensions folder

Resolution

To exclude unnecessary troubleshooting steps it's required to get the status of the restricted flag first. To do so:

1. Start Terminal: open Finder - Applications - Utilities - Terminal.

2. Type in ls -dlO /Library/StagedExtensions/ and hit return (Enter).

   NOTE: in -dlO O is a capital o, not the figure zero.

3. If the output of the command above doesn't contains the word restricted, proceed to the solution two.
   

4. If the output contain the word restricted proceed to the solution one.
   

Solution one

To troubleshoot the inability to start Parallels Services upon launching Parallels Desktop, perform steps outlined below one by one:

1. Restart the Mac and try launching Parallels Desktop again.
2. If the first step hasn't fixed the issue, uninstall Parallels Desktop.
   NOTE:  Restart is required to finish the uninstall process.
3. After restarting the Mac install Parallels Desktop again. If required, download the installation image from the Downloads for Parallels Desktop page.
4. Try launching Parallels Desktop again. If the issue still persists, do not close the notification window and submit technical report.
   Then contact the Support team for further assistance including nine digit technical report ID in the request.

Solution two

Parallels Desktop Engineering team along with the Apple Engineering team investigating this issue and for its resolution additional technical information needs to be collected.

Contact the Support team for further assistance. While creating a ticket, provide the output of the command ls -dlO /Library/StagedExtensions/  to make the further troubleshooting more productive.