No sound:
Check if the channel is muted.
Check the fader level.
Check routing.
Check the output connection.
Check amplifier power.
Feedback:
Lower monitor volume.
Reduce microphone gain.
Adjust EQ.
Move microphones away from speakers.
Distorted sound:
Lower input gain.
Lower output levels.
Check for clipping indicators.
Cannot find a channel:
Check the layer.
Check channel assignments.
Confirm the input is patched correctly.