Acrylic engraves very nicely, with the exception of clear although if you leave the protection paper on it will work too. Since you are doing pen blanks, it may be worth adding a rotary axis to your machine, there are several ways to do this. You will find some great examples over on that "other" forum
I had an issue with the Eleks A3 Pro where the laser would never turn on. I tested the laser output from the Mana SE board and found that all was good. I then discovered that the cable reversed the Vcc and PWM pins. That is the +12 Vcc (red wire) on the controller was wired to the PWM pin on the laser and that the PWM (white wire) on the controller was wired to the Vcc pin on the laser. The ground (black wire) was correct. I used a jeweler’s screwdriver to carefully remove the red and white pins from the plug on the laser end of the cable and swapped them. The laser now functions correctly.