Horse cannot return from nether

I finally found a good horse, and built a track through the nether to get it back to my main base. It went through the portal into the nether instantly, but after reaching the other end of the track, (an already established portal) it was unable to cross back to the overworld. I have tried using leads, riding it in and dismounting, blocking it in, and pushing it in. I have closed and opened the game several times, taken the horse away from the portal for long periods and remade and connected the portal, increasing the dimensions to help it through.