This is whats happened to my friend & her mare too!
She was out in the paddock for two hours trying to get the darn thing on her.

My horse was somewhat like that, but with a lead shank.
Someone must of smacked him with it in the face & he was scared of it...
So, I would just go out & play with him for a bit & get his favorite treats & feed it with my hand that had a lead rope tied around me...
At first he bolted off but then he started getting confidence.
Another thing I did was put some leads by his water & food dish out in this paddock.
So he would notice it wouldnt do anything when he was eating or drinking.
Then I would let him see it,bite it,etc & then I would rub it on his face,shoulder,withers,rump-etc..
& I would do that for ten mins each day.
Now he has no problem with it