Q.Why did my tulips not bloom?
I planted Tulip bulbs in the fall, the leaves have come up but they are not blooming. The leaves are beginning to die down on some of them. It may be possible that our winter here was not cold enough, but I’m really not sure why they didn’t bloom. Should I dig them up and replace with new bulbs in the fall, or leave for one more season to see if they will bloom next spring?

Certified GKH Gardening Expert
This is common for tulips, unfortunately. Tulips are finicky. If you are lucky enough to live in an area that is their perfect environment, they will bloom for years, but if you don't, they mostly only last a year or two. In some areas of the country, they are simply treated as annuals.
Tulips like dry, hot locations in the summer and cool locations in spring and fall. If they do not get this, they don't like to rebloom. These articles should help: https://www.gardeningknowhow.com/ornamental/bulbs/tulips/tulips-bloom-every-year.htm
https://www.gardeningknowhow.com/ornamental/bulbs/tulips/tulips-care-and-tulip-planting-tips.htm