This can be caused by several different things. First, ensure that the computer still currently recognizes the sound card, and that the drivers are working correctly. Next, check all physical connections, and ensure that inputs are properly wired into the audio card input. Next, run the ASI Mixer application. If not currently installed, it can be downloaded from http://audioscience.com/internet/download/apps.htm In the ASI mixer application, check each of the inputs, and verify that the level indicators show that a sound source is currently active. Verify that Inputs are set to Analog or Digital where appropriate.