It is possible to control your devices with Siri in two ways:
A. Using the Siri shortcuts app
Then log into your account on the Smartnest App. Then Open the Siri shortcuts App and create a new shortcut.
Then add a new action and look for the Smartnest App
You can either control the power state of any of your devices or lock or unlock your doors.
Then select the device you want to control and select the new state you want to set. (If you cannot see your devices try to kill the Smartnest app and launch it again)
Give the shortcut a name and save it. You can even add your shortcut as a widget to be able to use it from your home screen.