Patio umbrellas with pulleys should have a hole and pin system.  These usually have at least three holes where you can place the pin and adjust for height.  Sometimes it can get lost underneath the hub as you lift the umbrella canopy.  Try pulling a little bit more and see if you see the holes.  The canopy should "give" a little, so don't be afraid of pulling too much.  However, you should still be carefull, as not all outdoor fabrics are made the same as Sunbrella .