How to change marshmallow notifications and viberation setting
The vibration is part of the notification, so if you turn the notification off, you don't get the vibration. You need to turn notifications back on. If your phone is in vibration mode then the notification will make your phone vibrate instead of making a noise, without you needing to change anything else. Even if your phone is in noisy mode, you can change the options in each app individually so its notification only vibrates without playing a sound.