iPhone or iPad Home button is known to become unresponsive over a period of time, wherein some button taps do not register any input due to processing delays and lags that often result in an unresponsive behaviour, forcing users to tap the button multiple times. However, such an issue can be easily resolved by recalibrating your iPhone or iPad's Home button.
How to recalibrate your iPhone's or iPad's unresponsive Home button
Step 1: Launch any iOS app such as Stocks, Weather, etc that comes pre-installed on your device.
Step 2: Press and hold the Power (Sleep/Wake) button until the "Slide to power off" message appears on the screen.
Step 3: Now release the power button and press and hold the Home button until the "slide to power off" slider disappears.
That's it. Any open app will be terminated and the home button should now feel a lot more responsive.
Folks at iPhone Hacks have confirmed that the aforementioned recalibration method has been successfully tested on an iPhone 6 Plus and it certainly makes the Home button more responsive. iOS users must note that the procedure works fine on iPad and iPod Touch Home buttons as well.
Alternatively, you can resolve the issue using Assistive Touch via Settings > General > Accessibility section, which enables an on-screen or virtual Home button.
[Source: iPhone Hacks]