If the CLR doesn't work you can "with appropriate caution" use sodium hydroxide aka red devil lye. Just remember the three A's....always add acid. That means add the acid to the water, NOT the water to the acid or you could be disfigured in a bad way.
You can also unscrew the tip of the nozzle, where the mesh is, and unclog anything that may have found its way up there. In my case, it ends up being little balls of dog hair that drifts into the reservoir bucket. Sometimes it's a little "lint" on the mesh and not an accumulation of hard water deposits or whatnot.