The 450nm laser won’t work on clear acrylic (PMMA), because PMMA doesn’t absorb above 400nm
(see absorption spectrum for PMMA) PC, PET and PVC won’t work for the same reason. A good trick is to look up the UV transmission/absorption diagrams of the material and choose it accordingly. After a quick search I found some transmission diagrams. (bad quality but readable)
https://www.idec.com/auen/technology_solution/our_core_tech/images/264_image001_en.jpg
You can either choose a different material like PP or HDPE or you can coat the surface with paint (white should work too, but might need more power / time)