A:AnswerIt's possible that the internet output signal may be muted from the actual website, or you may need to assign the output from the source of the signal, and add device as an audio option source.
A:AnswerYou may use any headset. However, it will need to have a wired connection to the small receiver that is provided with the Flex 5000. I"ve used my Bose and Sony Headphones with mine and both worked great.