I assume you are prebaiting? Kind of warm right now, so if you are not using something that is preserved and will stay that way, the bait could be rotten and the foxes are thinking "yuck". Possums would like it though LOL.
Right now I would just dig beds and sift out rocks. Maby dig a dirt hole, but no bait of any kind. When the trap goes in then you can bait it. Otherwise you will get a lot of non-targets-i.e. Grinners and Poecats. Best to save bait untill cold weather.
i have a cam set up and was trying different lures to see a response triple dig it was the lure and 3 red foxes and a coyote left there mark there all in one weeks time the coyote was the last to do it fyi cavens hyawatha valley lure the reds dectroyed the hole