Sometimes you have them so confident that hen is there, that they wait for her to show up...next time, try not to call as much when you know he's/they are coming...this way you have them guessing where she is, and they're more likely to come and take a looksy...

but when they gobble, give a soft yelp or do some purring to let them know you are waiting, but then just set the call down and wait... good luck...