This has been driving me nuts. I have no idea when this started to happen but it is freakin annoying. if I call my horse, than mount it, start moving forward and than press shift (to gallop) it does nothing. The horse does not gallop and the blue bar at the bottom left of the screen that shows the stamina of the horse does not appear.
If I am running and than call my horse and mount it while I am running, the horse is galloping and the blue bar at the bottom left corner of the screen does appear. But if I stop at any point and try to gallop again when i press shift, the horse does not gallop.