lilac not blooming

Question

Last year there was a late frost and they started to bud but did not. This year there are only a few flowers.

Answer 1

While the most likely cause for your lilacs not flowering is the cold, both last winter and this one, there are other possibilities you might want to consider: https://www.gardeningknowhow.com/ornamental/shrubs/lilac/lilac-bush-not-blooming.htm