Hi, 

Unfortunately the photo you attached didn't come through. You can try to send it again if you'd like. 

There are a number of reasons why they produce foliage growth but do not flower. 

Is this the first year they haven't bloomed, or is this a re-occuring problem? It sounds like they have sufficient sun but it could be that they need more to bloom (probably around 6+ hours is better).

It could have been due to the cold dormancy. They need to be dormant for 6-8 weeks to bloom, but that should have happened this winter. 

Maybe they are planted too deeply?

Maybe a vole, mouse, chipmunk, got to the bulbs and gnawed on them. It could have damaged them enough to not bloom but still produce top growth. 

Maybe they have gotten too crowed. 

Do you remove the greens too early and the bulb can't restore enough energy to produce flowers? 

Are they in an area that is too wet?

Do you fertilize? If so it could be that the fertilizer is too heavy in nitrogen which would produce a lot of leaf growth. Bulbs shouldn't need any specific fertilizer. If you haven't applied fertilizer it could be the run off of any fertilizer that comes from the lawn. Instead just general use of compost, leaf litter, or bark mulch to add organic material back into the soil should be sufficient. 

According to Iowa State extension, tulip bulbs tend to lose their vigor after a few years and the bulbs become week and will no longer bloom. 

You can try to dig them up and space out while the foliage is up and see if they come up and bloom again next year.

The following website (while not Extension based) has some clear explanations and potential solutions to try for get them to flower: 10 reasons bulbs are not flowering

Michigan State University Extension has a more in depth webpage for reasons and solutions as well.

If you would like to try to send the photo again, feel free!

Emily