Clogged probally. If not it is a mechanical part failure other than the diaphram. Take the bar cover off. REMOVE THE BAR AND CHAIN. Clean out the little hole that pushes oil into the bar. Start the saw and rev it to see if anything comes out. If not drain the bar oil and clean out the resevoir with some brake clean to remove any foreign objects. If it still does not oil evaluate the pros and cons of having it repaired or buying a new saw. As it will probally be relatively inexpensive to replace it.