Some iPhone 6S users find problem with their 3D touch. If 3D touch function is work normally, you could gently or hardly press down the screen to get different functions in some apps within your iPhone 6S. Some users report that they cannot use the 3D touch function.
This problem is quite disappointing because they cannot use this feature while this is the prominent feature offered by iPhone 6S. It is important to remember that this 3D touch feature could only works in some apps and on iPhone 6S or iPhone 6S plus as the new hardware from iPhone.
If this problem is also happen to your iPhone 6S, you can try to fix it by choosing one of these several potential solutions. One of those potential solutions is by ensuring that your 3D touch option is active. Make sure that it is already turned on by taping the Settings, then choose General, and tap Accessibility, and then tap 3D Touch.
After you make sure it is already turned on, you also can change the sensitivity level in this setting then see if there is any difference after it. You can check it by pressing down an image, and if it works normally as a peek, it will give you a preview on web links or in emails.
Then if it works normally as a pop, after you press down harder an image, it will take you through the links or into the email. You must press it harder to go beyond the peek and the pop and usually it needs simple practice or you need to put your device on a hard surface to give enough pressure when you press it down to go beyond the peek and the pop.
If those steps are not working, please try to reset your setting by tapping the Settings, then tap General, and choose Reset, then tap Reset All Settings. Other option is by ensuring that all the apps are fully updated, because it could be the solution when your problem is caused by a specific app.
If resetting your phone and updating all your apps are still not working, you can try to use the Factory Reset option as the last choice to overcome your problem.