Baking is weird, some recipes allow for a mess up factor and some don't.
I personally have not had any problems with anything here, but then I have been a pretty adept cook most of my life and can usually salvage most things. That and lived in so many countries I am used to subsitutes.
Azroomie, the advice given is good and hopefully the next batch with lemon extract wil come out great.
Sometimes it can be things like the age of the flour, baking powder or quality of ingredients. I have had a loaf or two of bread just not rise for whatever reason.
I would suggest that a possible alternative to the use of lemon extract would be lemon zest... alternatively take a bit of vodka or other light tasting alcohol and soak the zest of a few lemons in it for a few weeks.
Another thought is to use a fwe spoons of an Italian liquor called Limoncello. It's readily available and is used in baking all the time...
http://www.limoncello.co.uk/acatalog/Limoncello_Limoncello_9.html(also not a bad source for Provolone!)