In my experience with remote IR sensors the problem 9 times out of 10 is that the re-emitter is too close and is overloading the sensor. This is especially common if you are installing the amp in a cabinet say and don't have much room to operate
The sensors in ARC kit are pretty sensitive, for example they work well when I used to bounce my IR signal to my Ref 40 off my speakers!
Does the extension work with the cabinet doors open and the re-emitter 3' or more from the amp? If not then there may be a problem with the re-emitter, can you test it on another component?
If it works have you tried mounting the emitter on top of the amp and in effect bouncing the signal off the inside of the cabinet? This often works well I've found
Anyway knowing more about how you have the system configured could be helpful.
The sensors in ARC kit are pretty sensitive, for example they work well when I used to bounce my IR signal to my Ref 40 off my speakers!
Does the extension work with the cabinet doors open and the re-emitter 3' or more from the amp? If not then there may be a problem with the re-emitter, can you test it on another component?
If it works have you tried mounting the emitter on top of the amp and in effect bouncing the signal off the inside of the cabinet? This often works well I've found
Anyway knowing more about how you have the system configured could be helpful.