Could be any of several things:
1) they didn't get enough chilling. Tulips are generally rated for zones 3-8 and it looks like you are in zone 8. That means that you are right on the edge of where they can grow. If you had a slightly warm winter, they might not have had enough chilling.
2) they were just spent. Many tulips are grown as annuals, just dig them up and compost them after they bloom. Look for tulips that are specified as long lived or for naturalizing. Darwin Hybrid tulips are one variety that will come back and bloom, year after year.
3) the bulb didn't store enough energy to make blooms. Be sure you leave the leaves on the plant until they have turned brown and withered. When they do bloom, cut the flower stalk off after the flower is done so it doesn't make seed. Be sure it's planted deep enough and feed it with compost or bulb food.
Here's a reference: