I am working with Bailey too, trying to get him to retrieve things. He does the same thing, but we are having some good success rates with making sure the "game" is the funnest sounding, high energy for all, game!
I get "stupid" excited about the "fetch" process with him ( if i had neighbours they would prolly have me commited
)
at 6 months your pup still has some what of a short attention span, and there are so many other things that are fun too... ( to them anyway) so make sure that the game of fetch is the funnest possible thing going on at the time.
Its working here,
hope it helps you out too.