I've got an old CS24B and it supposedly it's good for 200 yards with good line of sight. Never had it that far, but I've done 100+ and didn't give it any thought.
Make sure you got a good battery in your remote and antenna seated good, check for bad solider joints.
I did some looking and your remote is also rated for 200 yards in ideal conditions, I say you have something wrong. Call FOXPRO, their customer service is said to be outstanding though I have no personal experience with it.