Jim,
I have NEVER seen good results with latex through an HVLP or cup gun...Oh, I'm sure you'll find those that have and even swear by it, but the solvent used for latex is
water, and water is nearly impossible to predict through a device using that small an orifice with that low of pressure...The paint would have to be thinned to a virtually unuseable consistancy, meaning a new definition to the term "multiple coats"...And the atomized paint will want to start to dry as soon as it hits that air jet at the tip.
...But you shouldn't be getting
nothing...Check all the ports and airpaths for blockage (latex will dry fast enough to cause this), and look for any factory labels or tags that you might have forgotten to remove...
Cupguns and HVLP were developed to deliver solvent based coatings. If you get one to work well with latex I commend you...I worked with a painter once, who on his first attempt at working with an HVLP tried to paint doors and trim with a latex semigloss enamel...The first couple of jambs didn't look too bad, but once the air started to get warm the paint came out of that gun like silly string...Took an hour to clean out too...
...Wish I were more help