I have created multiple line styles in a RSC file which have materials added to them, eg fence (timber) cyclone fence (steel) it shows up in the file that I created the line styles in when I go into LumenRT (works excellent). When I open a new file and use the line style there is no material attached only the colour (default)
Can you share the screen recording of the workflow?
That will give us more idea.
And also if you can share the file with us.
how did you make the material assignments? A rsc file does not store a material assignment as this is usually done in the level manager.