Appears to be a full tin so, its not that it has dried out. Stir well and it may regain a normal consistancy. Could try adding a small amount of water to thin it. Emulsion is water based anyway..
Get a paint mixer, in a cordless drill, a 2.4 tig filler rod, cut to size, works a treat, (Or something similar), test on wood, concrete, whatever, then decide, when it's dried, is it good/bad.