That’s strange. The default device for the monoprice switch is z-wave switch which I appended the configure button to from the aeon multi sensor I think. If you already used the configure button once you can switch back to the official Smartthings z-wave switch. Very little effort was put forth on that device type so I’m shocked it broke for you.
I will take a look to see if I can reproduce the issue.
On another note mine seems to be working fine, which doesn’t bode well for your “location.”
Edit: still works fine for me. Maybe remove the device from your hub and try again?