Unable to turn off Popp Z-Wave outlet switch

I have been given a Popp Z-Wave outlet switch.
I have configured it ok but cannot turn it off in the ST app. I can turn it on ok in the app and can also turn it on and off manually using the button on the device.
Does anyone else use this device and if so do you have any issues.

Here is the device in question.
http://www.vesternet.com/z-wave-popp-on-off-switch-socket

Im aware of just how old this is, but Im having the same problem with this myself and wondered if you ever solved it? So strange that manual control is totally fine, its just ST will only turn on, you cannot turn off through ST…

This is the only topic I can find discussing this problem…