All TFD licenses allow use of 3rd party renderers. This must be a technical problem.
There is a known issue in the current Redshift versions that prevents it from finding TFD unless it is installed in the (old) C4D plugins folder. That is, TFD must be extracted into the folder
(Windows) C:\Program Files\Maxon Cinema 4D R2x\plugins
(MacOS) /Applications/Maxon Cinema 4D R2x/plugins
If this folder does not exist, you can simply create an empty folder with that name.
Also, the TFD folder must not be nested inside another one. That is, after extracting TFD, the .xdl64 (Windows) or .xlib (MacOS) files must be at
(Windows) C:\Program Files\Maxon Cinema 4D R2x\plugins\TurbulenceFD_C4D_v1-0_1465\TurbulenceFD_R2x_1465.xdl64
(MacOS) /Applications/Maxon Cinema 4D R2x/plugins/TurbulenceFD_C4D_v1-0_1465/TurbulenceFD_R2x_1465.xlib