Originally Posted by SebaKL
Make sure you press and HOLD, till the screenshot happens.
Don't just press and let go.
Or, as Hawker suggested, use the palm swipe:
System Settings - My device - Motion and Gestures <slide the toggle button to turn it on> - touch the Palm Motion text to enter sub menu, where you can select Capture Screen.
Thank you Hawker and SebaKL, really appreciate it, will test it.