Starry Night is set by default to read only 150 comets at startup from the comets.txt file. Unfortunately, new comets are at the BOTTOM of this file which currently contains 190 entries. Navigate to File > Preferences > Startup/AutoUpdates. I set comets, asteroids, and satellites to 600 to be sure I don't miss any.
I have Starry Night Pro v5 and have it set to download new data each time I launch it. It showed comet Mc Naught quite prominently. Unfortunately, try as I might, I was just not able to catch it for real.