Perhaps the compost is dried out, turn it out and mix it up with some fresh manure. Put it back in your compost container, water well and tread it down to help it heat up, cover with a sheet of polythene, if you haven't got a lid.

If your containers don't have vents--or you don't have containers--be sure to punch a few holes in the polyethylene to let air in, or it will stop composting and start stinking. Also, is this the same compost you had in December? If so, it may be past time to sift it, use it, and start a new heap.