It seems that in both 2.17 and now 2.25 the corrugated metals are not downloading properly, per uploaded image. Is this a Carrara limitation? Hope not.
Curious! In the shader room there is "none" but the render engine works fine...
My Rig: PC with AMD FX 8350 @ 4,00 GHz Win 7-64 Nvidia GTX 760 Nvidia GTX 970 (only for rendering) About 6 TB of disk space (768 GB of SSD) Octane/Octane for Carrara
The problem with these materials is that they are nested inside a double layer of node graphs. I don't know why the poster did this but it seems to confuse the Carrara plugin. I may or may not be able to work around this. I doubt I can get to this for a couple of weeks but I will look into it.