Dimming this ~30V led with PWM, what do I need?
It will not be possible for you to PWM dim your LED with that LED driver (power supply).
That is a constant current driver with under/over-voltage protection. It delivers a specific amount of current (1.5A) and varies the voltage to allow that to happen.
If the voltage rises too high or falls too low then there must be a fault, so it shuts the power off. This is usually because there is either a short (LEDs tend to &quot;fail short&quot;) or an open circuit. The former causes the voltage to drop too low and the latter for it to be too high.
When you insert PWM control you alternate between driving the LEDs and an open circuit. If that open circuit persists too long (low duty cycles) the driver will shut off.
You will need to replace the LED driver (the power supply) with one which includes PWM control internally to it.