I also cannot understand why this would work on Uno and not work on Nano. So you must post the schematic and post the code in code tags as described in the forum sticky post. (Most forum members read the forum with smartphones and tablets most of the time, so cannot open a .ino attachment). Also please post pictures of the circuit using the Uno and the circuit using the Nano. Make sure they are close-up, well-lit and sharply focussed, and neat enough to see where all connections are going.