If you are experiencing problems with your F4 these will typically be resolved by resetting your phone and re-pairing with the F4.
You can reset the F4 by holding down the Multi-Function button for 40 seconds. This will clear any pairing information and reset the device to the factory defaults.
If the F4 stops responding to your button presses, you can reset it by connecting the device to the battery charger and waiting for a few minutes.