Why didn't any Pokemon spawn when I used Incense?
Incense should guarantee a Pokemon spawn every 5 minutes when standing still, or every minute if you continuously move more than 200 meters away from the previous spawn. (Source). In other words, with a run time of 30 minutes, Incense should guarantee 6 Pokemon spawns minimum during that time.
The issue you encountered was likely a server connection issue at the time in 2016, during the initial spike in player numbers and a lot of weird server issues plaguing the game at the time.