Can't get two Grove atomization units to work with simple wiring

I purchased two Grove atomization units from Digikey in the United States. They arrived today and I wanted to test them without code by simply connecting VCC to 5V, Gnd to GND, and EN to VCC. Nothing happened, except if I unplugged the piezos, the boards heated up. So they seem to be kind of working but something isn’t right.

Any insights, something obvious I’m missing.
THanks

Hi, @dduehren:
there exist a guideline in our wiki that can help you how to use it.