Hi,
I'm sorry to hear you're facing trouble with it. Curb styles use the spline's Material IDs to assign different types of curbs (ID 1 for normal curb, ID 2 for drop curb), so feel free to set the corresponding part(s) of the spline to the appropriate Material ID. Let me mention that, as posted here on our forum:
"... upon my experience, in case of importing splines from a .dwg file, its Color is used for generating the 3ds max Material ID. If you want to avoid the Edit Spline modifier step - assigning the Red color to such spline (layer) should result in ID 1 / Yellow as ID2 (as the Red color should be indexed 1 (Yellow 2) in AutoCAD)."
I hope that helps.
Best regards,