Resolution

1. Run TextEdit (or any other text editor you prefer), click on File -> Open,

2. Browse to the root of your Mac disk -> Library -> Preferences -> Parallels folder,

3. Select dispatcher.xml file to open in editor,

4. The license and owner details are enclosed in <License> tag in the beginning of the dispatcher.xml file, for example:
 
   <License>
      <Key>AAAAAA-BBBBBB-CCCCCC-DDDDDD-EEEEEE</Key>
      <User>Your Name</User>
      <Company>Your Company Name</Company>
   </License>

in the above example, AAAAAA-BBBBBB-CCCCCC-DDDDDD-EEEEEE is license (activation key) installed on your Parallels Server.

Alternatively you can retrieve the License (activation) key using
 command line:
 1) start Terminal
 2) paste the following command:
  grep -A4 '<License>' /Library/Preferences/Parallels/dispatcher.xml

 3) find the license AAAAAA-BBBBBB-CCCCCC-DDDDDD-EEEEEE in the terminal
 output similar to this example:

macserver1:~ root# grep -A4 '<License>' /Library/Preferences/Parallels/dispatcher.xml
  <License>
     <Key>AAAAAA-BBBBBB-CCCCCC-DDDDDD-EEEEEE</Key>
     <User>Your Name</User>
     <Company>Your Company Name</Company>
  </License>


5. Close dispatcher.xml file. Please do NOT do any manual changes in the file!