Wayne, maybe it's the approach? One of mine won't bite, but shies away and runs off when I try to put her harness on her. I think it is also something in her mind.
The consistent approach that has worked for mine is: I sit on the floor, call her, and say, "treats!" (armed with some, of course :)). I ask her to sit, praise her, and then when I put the harness over her head, I don't reach over her head, I place it below her mouth and gently put it over her face. Again praising, coaxing, gentle voice, and a treat. When I remove it, it's the same thing.
Good luck! Let us know?