Some citrus trees can be a bit slow to get going, you have to patiently watch them grow for several years before you get any fruit.

Having said that, plants need phosphorus and potassium to set flowers and grow fruit. Fertilizer (or compost) that is high in nitrogen will give them plenty of lead growth but won't help with flowers. Giving them a dose or two of an organic fertilizer for veggies and flowers will help.