[SOLVED] Unable to retrieve /templates/jp-rooms/less/custom

I try to customize JP-Rooms but I get the message "Unable to retrieve /templates/jp-rooms/less/customizer.json (Not Found)"

I tried a clean installation of the template and also the demo content of the same template. - Same error on both Joomla systems.

I run Joomla on Windows Server / IIS.

The requested file exists in the file system.

[Troubleshooting] Warp 7 Customizer: "The current theme is not customizable.", "Retrieving Styles Data Failed", "Unable to retrieve" & related errors
yootheme.com/support/question/75099

Problem solved.