Sounds like your training sessions are low distraction and high attention. The dog knows it's working time, and is "on". But the dog hasn't learned to "work" in any other context.
Once the dog "undersstands" the command, you need to start proofing. Working with slowly increasing distractiosn and in new places. Make sure to take a step back when you add either new envrionments or distractions. There are three d's in training: distance, duration, distractions (which includes "new places/situations" as well as people, sounds, other dogs, birds).
Recall when a PUPPY is palying is pretty much the epic of distraction. Take baby steps to get to that.
In my books (and not a trainer nor a do I compete in field or hunt trials) - bofore you introduct the eocllar you need to keep working ont raining by working in the three d's slowly. Actually EVEN if you add the ecollar you have to work in the three D's into training. You have to practice and teach before you correct - and there are parts missing in the training here.