Download the Adobe PRTK tool.

Open Command Prompt as an Admin, and navigate to the Adobe PRTK folder.

Run the following command to generate the prov.xml file:

Windows:

adobe_prtk --tool=VolumeSerialize --generate --serial=1155-XXXX-XXXX-XXXX-XXXX-XXXX 
--leid=V7{}InDesignServer-15-Win-GM --regsuppress=ss.

Mac:

adobe_prtk --tool=VolumeSerialize --generate --serial=1155-XXXX-XXXX-XXXX-XXXX-XXXX
--leid=V7{}InDesignServer-15-Mac-GM --regsuppress=ss.

After the above command runs, the following message is displayed on the terminal or console:

Return Code = 0.

It generates the prov.xml file at the location of the Adobe_prtk file.

Note: LEID depends on the version you are trying to install. Refer to the following information on LEID  for various Creative Cloud versions: 

Creative Cloud
leid=InDesignServer-CS7-Win-GM
leid=InDesignServer-CS7-Mac-GM

Creative Cloud 2014
leid=V7{}InDesignServer-10-Win-GMleid=V7{}InDesignServer-10-Mac-GM

Creative Cloud 2015
leid=V7{}InDesignServer-11-Win-GM
leid=V7{}InDesignServer-11-Mac-GM

Creative Cloud 2017
leid=V7{}InDesignServer-12-Win-GM
leid=V7{}InDesignServer-12-Mac-GM

Creative Cloud 2018
leid=V7{}InDesignServer-13-Win-GM
leid=V7{}InDesignServer-13-Mac-GM

Creative Cloud 2019
leid=V7{}InDesignServer-14-Win-GM
leid=V7{}InDesignServer-14-Mac-GM

Creative Cloud 2020
leid=V7{}InDesignServer-15-Win-GM
leid=V7{}InDesignServer-15-Mac-GM

After the prov.xml is generated; run the following command:

adobe_prtk --tool=VolumeSerialize

It generates return code 0, and the InDesign Server is licensed now.