Facebook Messenger chat heads disappeared after installing Android 6.0 Marshmallow update? Well, it’s because of the new app permissions management on Marshmallow which is stopping Facebook messenger from putting overlay chat heads on top of other apps.

You can enable it back by doing this:

  1. Go to Settings » Apps » and touch the “Settings” icon on top-right corner.
  2. Select “Draw over other apps” from the Advanced options.
  3. Select “Messenger” from the list of apps.
  4. Toggle On “Permit drawing over other apps”.

That’s it. This will allow Facebook Messenger to display on top of other apps.