Ok, i am really worried now!!

At the close of the day today the 23rd day of incubation will have been and gone, and not the slightest hint of a chick in sight from the 12 eggs inside that i have nurtured for the best part of a month  

All has looked well from candling them at day 10 and day 16, i have turned them as advised, taken care of temp and humidity and most importantly left them alone. And still, nothing happens. An egg, the symbol of an unfulfilled promise.................

Having pulled myself together, does anyone think that it might be worth continuing - is there still hope?