Two beekeepers called me yesterday to tell me they have no brood and must be queenless. They both said they had pollen patties on. After a brief conversation both told me they had the patties in a place where the bees cannot easily get at the patties, and the bees were not eating the patty.
Pollen patties need to be placed right on the cluster of bees. If the bees can't mass around part of the patty, they won't eat it. If they don't have pollen, the population of the hive will suffer.