This is sort of the wrong forum to ask that question, but if it is large bed of them, and they have been there quite awhile, I'd suggest them might need divided. The mature plants put off lots of bublets and they take a few years to reach blooming age, but will produce foliage only.

which forum do you suggest?

Have you added bulb food at any point to feed the crowded bulbs?

If the daffs have never bloomed or only bloomed the first year where they are planted even though the greenery grows well, the chances are they are not getting enough sun. Add some bulbtone (or similar product) this spring before the leaves yellow.

Or you can dig up a few of the bulbs and see if they are smaller than what was planted.

Are you leaving the leaves until they yellow or are you braiding them or cutting them off before they yellow? If so, that's your problem, the bulbs can't make enough food to bloom again.

The bulb forum may have been a better choice. But all of the advice given is valid.

Yet one more possibility would be that they were planted too deeply in the first place. You may find that a combination of these causal factors contribute to the daffodils' poor performance.