Iris not blooming
I have had very limited blooming of my iris this year. The plants have not yet completed a circle, so I don't believe they are too crowded. This is true of both my regular irises, as well as my blue flag irises. I've had them for many years and they have always been prolific bloomers. The plants look very healthy and are receiving the same amount of sun as usual.
Wright County Minnesota
Most likely you aren't seeing any blooms because of the odd weather we've had. A freeze can kill any new buds forming on the plant. Freezes a month to a month and a half before blooming can cause the plant to abort the buds and you won't see any flowers this season, unfortunately.
While that is the most likely cause, I would recommend lifting one or two and checking out the rhizomes for any damage.