Yamaha RX-S601 Owner's Manual page 110

Problem
The unit cannot be controlled using the remote
control.
An input source cannot be selected using the
INPUT knob on the front panel.
The RED/GREEN/YELLOW/BLUE keys of the
remote control do not function.
Cause
The unit is out of the operating range.
The batteries are weak.
The unit's remote control sensor is exposed to direct sunlight or
strong lighting.
The remote control IDs of the unit and the remote control are not
identical.
The remote control is set to the Zone2 operation mode.
The "Input Skip" function has been applied to that input source.
The device which is connected to the unit via HDMI does not
support the function of the RED/GREEN/YELLOW/BLUE keys.
The settings of the RED/GREEN/YELLOW/BLUE keys of the unit's
remote control have been changed.
Remedy
Use the remote control within the operating range (p.5).
Replace with new batteries.
Adjust the lighting angle, or reposition the unit.
Change the remote control ID of the unit or the remote control (p.104).
Set the remote control to the Main zone operation mode (p.75).
Set the "Input Skip" function in the setup menu (p.97) to "Off" for that input
source, or select the input source using the input selection key on the remote
control.
Use a device which supports the function of the RED/GREEN/YELLOW/BLUE
keys.
Set the "Remote Color Key" settings in the "Setup" menu to "Default" (p.98).
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