Being an avid coyote hunter( I hunt most weekends and anytime I can get the time during the week)I would like to add a few tips as well.
Foxes are very shy during the daylight hours and are mostly nocturnal. You may have better luck calling at night with a red light. They also like very high pitched, active or "busy" type calls such as a woodpecker in distress call. When the sun goes down, a foxes behavior changes, He no longer thinks he's so small, and becomes very bold in his behavior. I have had them come right up to the tailgate on my truck during night hunting. Some have even went under the truck to hide when they finally figured the gig was up.
Foxes aren't as scent cautious as a coyote is, but they will usually try to get downwindof you due to them trying to figure out what that great free snack is, and why it is making so much noise. Once you get them in close, say 100 yards, switch to a squeaker or coaxer type call. They have very good hearing and can hear a mouse squeak in distress for a very long ways.
Once you get the spotlight on him, don't take it off. If you do, he will more than likely see you and be gone.
Best of luck with the fox and happy hunting!