Why won't my iPhone 6 slide open either to make a call or to turn off?

[iMore Question]

I can't slide phone open to turn off alarms I set. I can't slide phone open to turn the phone completely off.

 

[nikkisharif]

Try rebooting the device. Press & hold the power & home buttons at the same time until the Apple Logo appears. This usually fixes little quirks in the system.

 

[IAmSixNine]

Same thing has been happening to my 6plus since 9.3.1 update.
As nikkisharif mentioned, powering it off fixes it for me for a few days.