There are many possible things that could be going wrong, including that the tool altitude is set too low to have a visible effect per click. I prefer to use a selection tool to outline an area that I wish to change and then use the appropriate Tools>>Global Raise item to change the world.

I can't be much more specific because I'm not sure what version the FT demo really is and my installed version does not really reflect the end-user experience for the versions out there in the wild.