A grayed-out Home button indicates that the headset is not connected to the app. Go to Settings->Connection and verify that the headset is in the Paired Devices list. When the headset is connected properly a checkmark will appear. If there is no checkmark, tap the name of the headset in the list of Paired devices to re-connect the headset. Another way to reinstate the connection is with a short press on the headset’s Power button.