We have had many boughts with the fish trap over the years. Best advice is patience, don't feed for a few days, put the trap in, sit and wait. Last fish we trapped it took all of five minutes for him to go in the trap. Before that the fish in question didn't go in the trap until three hours later.
Try all different times, if during the day doesn't work, try at night or with only actinics on.
You can also use a bottle, cut the neck off and reverse it, fish goes in... can't get out. (Well some knew better... but hopefully your fish won't)
Good luck.