When you set the Audio Record to OFF, it will stop recording audio but will still record the video. Did you make sure the OFF was checked or selected as shown below?
As for the MUTE function, you could do a quick press of this button in order turn off the audio during recording. After pressing the MUTE button, you will see this icon (
) on the upper right corner of the screen.
If, during the recording, you want to record the audio, then, just do a quick press of this again and you could record the video along with the audio.
Let me know if you have any questions.
Also, have you registered your product and generated a support ticket with us? Please check your email for further instructions.