Sure it is not extruded plastic? You want cast acrylic for laser work. (do they sell the two color in extruded? Dunno…)
I tried some extruded just for the giggle, and yeah it pretty much melted instead of cut.
Weirdly, I also had some extremely thin (0.03) extruded from hobby lobby and it cut fine. I think because it cuts so quickly (being thin) that it does not focus long enough to slag it like the thicker stuff.