I’m anxious

No sound come out when I plug into mtrack jack

I recently purchased Mtrack Maudio. After a few tries, I was able to get sound off from the left hand side ( below m-audio) by inserting guitar cable in line input and then using reaper to monitor it real time in Mac 10.7.5.

I tried the same thing in line in on the right hand side ( below m-track) but no sound comes into reaper. Can you please help me with the problem ?
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