A Checklist of Causes:
Are you feeding with high-nitrogen fertilizer? The first number in the N-P-K ratio should be low; high N=no flowers, so bulb fertilizers aren’t high N? Use instead one, low in nitrogen with these numbers: 3-6-6 or: 5-10-10.
Did you neglect to feed for more than a year or two? Feed bulbs when they begin active growth - when the green shoots are emerging. Use an all-natural organic fertilizer intended for bulbs. Apply according to label directions.
Did you cut foliage back too soon last year? At least 6 weeks of “ripening” time is needed, with their foliage growing and intact. In order to hide these yellow leaves, plant the bulbs behind large perennials or shrubs. They will grow up or bloom at a time after the Daffodils are finished blooming.
Is the area very dry? Bulbs need ample moisture when they are growing actively. On the other hand, a soggy area is harmful to them.
Is the area filled with tree roots, or with other competing plants who grab all the nutrients and moisture? Areas under evergreens can be inhospitable, for instance (ad well as too shady).
Dividing may be called for - or transplanting to another, better-suited area.
Were the bulbs recently planted or recently transplanted? Both can set back the bulbs for a time.
With daffodils - and bulbs in general - there are some additional triggers of diminished bloom, says the American Daffodil Society. Read their full list of possible causes:
https://daffodilusa.org/growing-daffodils/non-blooming-daffodils/
What About Tulips?
They need similar care: In the spring, when leaves emerge, feed your tulips the same bulb food or bone meal which is low in nitrogen, the same you use for Daffodils: 5-10-10. Water well. Deadhead tulips as soon as they go by, but do not remove the leaves! Allow the leaves to remain on the plants for about 6 weeks after flowering.
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