You may need to make sure that your winterberries (I'm assuming Ilex verticillata) females have a male planted nearby that is actually the appropriate male to pollinate them--ie, blooms at the time they need. Not all males do that at the right time for all females. Any idea what varieties of Ilex vert. you have?

The mae may still be too young to flower well, or may be a poor match for your females. Or it may have been a bad spring for the pollinators, cold wet weather stops them flying about so much.

The flowers that should have been on the bushes this spring (did you see any?) would be set on the previous year's wood late in the previous season. So your pruning last summer could have affected this autumn's berry crop.

I have a few winterberries, both I. verticillata and I. veriticillata x serrata. That would be Winter Red, Winter Gold, Red Sprite, Bonfire, Oosterwijk and Sparkleberry. Several of them were just rooted cuttings when I got them and they already held berries. Maybe seed grown will take time to flower but I think plants of named varieties from cuttings will flower the first year. Apollo pollinates all except Red Sprite and Oosterwijk. A friend has Red Sprite with Raritan Chief and has yet to see berries on it also. This year I purchased Jim Dandy because the local arboretum has Red Sprite full of berries every year and that is their male that I noticed. However, because I purchased it from zone 7 in a greenhouse and I am in zone 6, it was already blooming when I purchased it. Won't know if it worked until this year. If you have Red Sprite, you might notice the bark is whiter instead of black. Thought maybe it was a mistake but the local nursery had Red Sprite with light bark too. There are charts available that match male blooming times with female blooming times. Forest Farm has one in their catalog. They list in 2002 as follows:
End of May to early June bloomers:
Males: 'Early Male', 'Jim Dandy'
Females: After Glow, Autumn Glow, Cacapon, Harvest Red and Red sprite
Early June to end of June bloomers:
Males: Apollo, Southern Gentleman
Females: Bonfire, Maryland Beauty, Sparkleberry, Sunset, Winter Gold and Winter Red
Hope this helps. They are worth the trouble.

Have 4 females, 3 Sparkleberry and 1 Winter Red. All are planted within seven feet of each other. A Southern Gentleman is located within the group with a Jim Dandy approximately 50 feet away. For the second year in a row the Sparkleberrys are healthy and loaded with berries but the Winter Red berries which had been abundant after flowering have turned black and dropped off the plant. It has been a dry summer and I have been watering every few days. The Winter red seems to show a bit more stress than the Sparkleberrys. Is it possible the Sparkleberry are a bit more hardy than Winter Red? Anyone have any similar observation?

No answer to your question, however, consider the frustration. Found unknown female at a great price years ago. Went years with only a dozen or so berries. Bought tiny Apollo male. That died, either from drought or being stepped on, or both. Bought foot tall 'Southern Gentleman' that coincided in bloom to female. Total load of big berries until last week. The first wave of migrating robins ate almost every one,leaving the native hollies mostly untouched. Will use bird netting next year, at least until the leaves are gone, or it snows. See bushes loaded all Winter locally, in neighboring swampland. Ya gotta laugh!

Well, at least you know your efforts were appreciated.

Ilex verticillata blooms on new wood, so pruning the bushes last year would not affect flowering this year. A very rainy period during bloom might well decrease the number of berries but I doubt if it would result in no berries at all. My guess would be either your male isn't a male or it blooms either earlier or later than your females.