We had lights on our ducks for a solid month this year before they decided to start laying, so it could still happen.  Actually, only 2 of the 4 girls are laying, but one has always been a bit gimpy and an unreliable layer, and the last one just does her own thing in all regards.  
Did you just set the lights once and leave them at a steady day length?  Morning or evening or both?  Now that solstice has passed, daylight is working with you, but in the fall, if you only have artificial light at one end of the day or the other, their overall day length is still decreasing as the natural light decreases.  We put the light on morning and evening, and added a half hour a week until they started laying.  (Then promptly let the light burn out.  Ugh.)
I've also noticed that egg laying often starts for us when there is a spell of "spring like" weather.  They also tend to engage in, um, spring-like behavior, then, too.  I know you don't need a male to have eggs, but I do wonder whether going through the motions of mating, even if it's just the girls, stimulates things.  Or maybe it's just a side-effect of the hormones that cause egg-laying.  But either way, believing that it's spring seems to be part of getting the egg-laying to kick into gear.  The weather this coming week looks really promising for that!
 
Christy