Hi Karl,
I do not think that it has anything to do with the license.
It should work in any case. Different between licensed and non licensed is only the limitation of points and may artifacts or noise.
If you have a license you just put this in the ./bin folder of LAStools.
ArcGIS Pro has to be configured to use this version and use the licensed version then as well.
So this seems an ArcGIS Pro or configuration issue.
Please provide (much) more information what you exactly did and do, present some screenshots,
and may we can help.
Best,
Jochen @rapidlasso