You didn't give much info about the area you are hunting, where it is located, thick brush, open country, farm land, ect.

First, are you getting into the area without the yotes being aware of your presense? driveing up to a 10 acre parcel in a 4x4 with glass pacs blaring, radio booming out the bass, slamming the doors, coughing and clearing the throat on the way to the stand while we finish off the last drags a cigar, ect will make the chances of a yote even being within a mile of the stand. Coyotes also are not too fond of deodorant and perfume.
Camo is a must. An open jar of skunk essence about 3 feet down wind does wonders. It also does wonders if you spill it on yourself and have to wear those cloths on the drive home.
Set faceing down wind,(wind blowing over your back) as the yote will circle around to get a smell on the critter making all the noise, and will approach from down wind. Be sure that you can see the coyote before he gets a wiff of your scent. If he thinks he smells a human, you will never see him. He will be in the next county in a couple of minutes. If your bait pile is properly placed, you should be able to approach it from down wind without being seen and can often take an unsuspecting yote or two feeding off of it. You may have taught the coyotes to avoid the calls you have been useing. Try a new, completely different sound that they haven't heard before. Poor callers can take a lot of coyotes IF the coyote doesn't know that a human is present. If they suspect human presense, the best caller want even see one. Good luck.