If you are confident that fox are in that area, in reasonably decent numbers, maybe it is not so much what call you are using but maybe other things. How is your approach to your stands? Are you skylining yourself on the horizon? Are you playing the wind right? Do you scan with your light the entire walk in? Not that it is ever easy, because as we know predator hunting/trapping can be very humbling, but this time of year for reds ( I can't help with Greys) simple squeaks or distress calls should work fairly well and at least produce eyes..theres a bunch of stuff on here to read and learn and many people on here with much more experience than me. Another thing, as we are starting to see a trend here this season where I hunt, coyotes can possibly be a culprit of not seeing fox. We are seeing less reds on stands and we have heard or encountered more coyotes than before. Is it a coincidence? Time will tell. Also, coyotes will often stay silent and not respond to vocals..they will simply just come in..and be gone..without you even knowing. Hope this helps a little. Good luck.