fishdaddy;
You have asked a WHALE SIZED question.
First: My first question would be-- are you sure you on the right locations? If you are not getting any visits or fox sign is not close to your traps, then I would look the place over carefully and find where the fox are moving. Look for trails, tracks, droppings, etc. Once your set location is on the money, you should start seeing activity. There are times when I get on my hands and knees (seeing at his level) to search for a salient feature. One that stands out to him and he can't keep from visiting. Chances are when you find that, you will find plenty of sign from him.
Second, are your traps "clean"? Avoidance is a problem often associated with a dirty trap.
Third, are you leaving to much of your sign where you are trapping?
Fourth, are you using a good urine or lure?
Let us know a little more information and maybe someone can help you.
The above pretty much applies to coyotes as well as reds. Since we don't have any reds here, I use the same standard for coyote.