Redshift volume shader greyed out


I am interested in TFD and trying the demo. But In the redshift volume shader all TFD options are greyed out. What is the problem?

Unfortunately, the Learning Edition does not support 3rd party renderers at all. I hope this restriction can be removed in the future, but for now there is no way to test the Learning Edition with 3rd party renderers.
The licensed version is supported by Octane, Arnold, Redshift and Cycles.