This happened to me the other day when I was working on the trailer, thus had it jacked up. The solution was to jack the rear of the trailer up so all wheels are hanging (tongue attached to truck for added saftey over the jackstand). Then lower the "good" wheel onto a block to bring the equalizer all the way towards it and give the offending shackle room to flip back over. Use a pitch bar to force the shackle the correct way. May need to lower the trailer or raise offending wheel to get it to take. I found it helped to have the opposite side tires free of weight as well to allow flexibility for this to happen.