If they've been eating and sleeping in the coop for 2 weeks, they should know it's their home. You can try locking them in for a little while, though.
Are the ones you're having to round up roosting outside or just continuing to forage?
Sometimes, a human's idea of when it's dark enough to go in and a chicken's idea of when it's dark enough to go in, are slightly off. We want to get them safely locked up and go do other things, since it's starting to get dark. They think it's still light enough to see, to forage.
Before they go in for the night, my chickens will often work their way back toward their coop, then wander off for a bit, then really go in.
I free range in spring and summer. When hawk attacks get to be too much of a problem in the fall, I keep the chickens in their pen. During that time, they only get supervised free range time, later in the day. If for some reason they get less than an hour, I notice they want to stay out later, to make up for it. If your chickens are only out for a short time, they may be resisting because they haven't gotten enough time foraging.
Until you get a stronger conditioned response to your training them to come back to the coop or run for treats, you may need to find a more tempting treat. Something they just can't resist! It also helps during training, to only be giving that treat when you call them in. If they have scratch available in the coop during the day, it's not as tempting as a treat when calling them in at night. Use a container they can see from across the yard and always use the same treat container. Training with a good bribe, should get them conditioned to go back in the coop/run at any time of day.
Hopefully, you'll figure out a way to get those little hooligans to behave better!
