Button pressable on iphone up to iphone5s, is not pressable on 6 or 6plus

I am having a problem I don't understand. I would appreciate if someone can guide me in what to look for to solve this.

I have a button (save) that for some reason is not pressable on iphone 6 or 6plus - although clearly visible and where it should be on the layout (both simulator and device) but works fine on iphones up to 5s

On both of this images I was trying to press the button.