Is there some hidden mold in it?  My cows will eat about anything except moldy hay. I would not knowingly put out moldy hay however there occasionally have been some bales with some internal white mold that was not visible from the outside of the bale. I must have gone through a wet spot or ditch with the baler and that hay was not as dry as the rest of the bale and caused a moldy internal layer in the large round bale.

Cows will sniff it and turn away as you describe. The cows will not eat these bales unless I cut off the moldy layers (if possible). When I run into one of these I usually end up using it more for bedding than feed.  Sounds like what you describe. Maybe dig into the bale a ways and see if you find some mold?

Good luck.

Jim