Answer: According to your zip code you are located in the coldest part of zone 5, zone 5A. There is a description of the winter hardiness zones and what they mean for gardeners at the following web page, you need to scroll down the page below the map for the detailed explanation.
Kwanzan is a flowering cherry variety that is considered to be winter hardy into zone 5. That means it would not be expected to do well in areas colder than that, and it would probably die due to winter cold in zone 4.
Since you are in the coldest part of zone 5 (and if your microclimate is cold and windy or exposed then it may be as cold as zone 4) it is possible that the winter cold is damaging the flower buds and preventing the tree from blooming.
Other possible weather related causes for flower buds to fail can include drought, sharply oscillating temperatures in the spring, and a hard freeze just as the buds are opening.
Or, since it is a new tree, and not yet fully established, it may not have formed any flower buds last year. Those buds would have opened this spring -- so if it did not have the energy to form flower buds last year then you would have no chance for flowers this year.
The buds for next spring will form on the tree during the current growing season. This fall, you should be able to look at the tree and see the flower buds for next spring. If you see buds this fall but no blooms next spring, then you can attribute the failure to the winter weather.
I hope this helps.
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