I bought a few of the Samsung SmartThings buttons and sensors during the Spark sale a few weeks ago.  I only got a chance to play with them over the last couple of days.  I have a problem with the buttons.  They don't seem to trigger the action that I set for them, although I can see that the buttons are registering presses.

I have a panel heater that is connected to a TP Link smart plug, which is in turn added to my SmartThings app and I'm able to turn it on/off just fine from the app itself.  I can also have a routine that works fine to turn it on and off at times of day.

When I set up the smart button I went through the usual process to get it recognised by the SmartThings hub and app.  I then made it do something very simple - basically turn that plug on/off when the button is pressed.  But that's where it doesn't work.  I can see the button presses coming up in the app, but it's not doing the action of turning the plug on/off.  

Any ideas here?  Seems like there's not much else I could do since it's such a basic setup.  I have tried two separate buttons too, so it seems like it's config and not device problems?