I have a 4th Generation I pod Nano that won't sinc with new Itunes. HELP!

I have a 4th generation I Pod Nano, and it will no longer sync with I TUnes. I downloaded the recent version of Itune. . . I can see my extensive library and see my purchase from yesterday. . . but I cannot sync that purchase to the NANO. The choice to sync is not available, and when I run diagnostics, it says no I Pod is connected even though it is currently charging. Does anyone have a suggestion??? Please?