Siri can't be instructed on iPhone 6/iOS9

I am using an iPhone 6 with the latest iOS (9.x.x) I would like to have Siri instructed so I can use it without having to push the home button. when the iPhone is connected to a power source. That doesn't work. When using the wizard to teach Siri to listen to my voice exclusively nothing happens. I need to repeat the 'He Siri' (i'm Dutch) a few times and after a few times the iPhone states that I was not understood so I should do it again. I tried it already 10 times but still no luck.

Anyone a clue how to solve this? When using the home button Siri works as it should. 🙂