Sleep Issues--HELP!!!

I'm sorry to be starting another of these threads, but I'm super frustrated. Every so often this seems to happen on all my Macs, where suddenly it will stop going to sleep. This time it will not sleep whether at scheduled time or when I tell it to sleep from the Apple menu. It started doing this today when I was trying to figure out a problem connecting my monitor to a Caldigit Thunderbolt Station. I'm running 10.9.1 on a 2012 Mac Mini. This is what I've tried:

reset SMC
rest PRAM
repair permissions
clear caches
reindex Spotlight
and finally reinstall OS

There is nothing in the system log related to sleep. I've simplified everything so there are no additional peripherals attached to the Mini, removing the Thunderbolt Station and putting the monitor back on the Thunderbolt port. I don't know what else to try.

 

Thank you thank you thank you! I've been through all of those in the past, but I'd forgotten about usung pmset to get at what is preventing sleep. Turns out it was Internet Sharing. I'd turned it on to attach a printer to the network through the ethernet port on the Thunderbolt Station. Never got it to work, but forgot to turn off Internet Sharing. People like you are what make Mac Rumors so great for solving problems!