Check that tuner is connected to sound card according to the instructions: internal or external audio-output of tuner must be connected to internal or external audio-input of sound card. Immediate connection of tuner to acoustic system is wrong.
Check that you connected only one audio-cable between tuner and sound card. Never connect both internal and external cables.
Check that you selected the same mixer and line in "Audio" settings of application as the sound card and the input where you connected the audio cable.