I got Rocky about a year and a half ago. He didn't retrieve much but loved tennis balls. I mean REALLY loved them (though his first love was CHEWING them). With abit of time he started doing well with retrieving...just for a few minutes at first then by the end of this summer he'd go and go and go....he'd play fetch for over a half hour and could easily be coaxed back up if he went off to chew.
By fall he'd lost interest in fetching. Not even a good tennis ball could get him going. And now - some days he'll chew a ball others he won't even do that.
Normally I could deal with this but we've gotten involved with Flyball. The dog who was tennis ball obsessed and would go crazy when you pulled it out won't even blink at the ball. Not even for a treat.
Could he just be being plain stubborn? maybe the pressure of Flyball training has got to him? although I am not exactly an expert on Flyball, in field work if a dog is pushed beyond his or her limits they can effectively 'shut down'. From what I have seen Flyball is quite intense and energetic -- maybe he can't keep up? while I am certainly not saying a Lab can't compete in Flyball (far from it -- I bet my crew would love it!), it takes an intense sort of dog to excel in that kind of sport...
Are you still Flyball training? maybe taking a break from it will bring back his drive. After a break (a few weeks with ZERO retrieving) you can start building the foundations again...starting with one successful retrieve a day, then 2, then 3, etc.
I have to agree with trickster. LUCY was the one showing the drive for retrieving birds. It was LUCY that got us into hunt tests and it was LUCY that got us to search and own a pb chocolate with hunting lines. Before we went to Baja, Lucy was showing no enthusiasm, no desire and no drive for the birds especially in a Hunt Test situation. The pressure had gotten to her. For 2 months we didn't do any field work. I took her out to the field for the first time 2 weeks ago and she is showing drive again. If I can just keep the drive going and get her a Senior Hunt Title this spring, I will let her be a couch potato. Yeah, the titles are for me, but her and I have come this far and we are 3 legs from a SH for her/me.