There are several reasons why a citrus tree will not set buds but a cold winter is the most common. Too much water and lack of nutrients in the soil is also to blame. Try feeding your tree with an application of Osmocote plant food now and even though it may be too late for buds to produce this year the Osmocote complete fertilizer supplies  the tree will nutrients that make it more likely to thrive this coming winter and produce flower buds for next year. Do not prune off the new growth next year as severe pruning can also contribute to lack of buds. Let us know how things work out next spring, Keep growing, Marianne Binetti