[CMake] project not found despite being found

[Biddiscombe, John A.]

I have a project which generates a project-config.cmake file and a project-config-version.cmake file in the relevant place,
When another project tries to find_package it, I receive this message from cmake

"
  Found package configuration file:

    /Users/biddisco/build/cmakesuper/xxx/xxx-config.cmake

  but it set xxx_FOUND to FALSE so package “xxx" is
  considered to be NOT FOUND.
“

Which is not expected. If I set xxx_FOUND in the config, it goes away, but I was under the impression that the cmake find_package command itself should set the xxx_FOUND internally and not be done by the user.

Is the find_package command trying to tell me something by showing this message?

Thanks

JB