I found this, "Most blueberry plants will produce a small harvest by their 3rd year, but won’t really begin to produce fully until about their 6th year"
What I have done to encourage flower
production on some of my reluctant ornamentals was to dig around the roots as though I was planning on digging up a rootball. Not under the bush roots but around. It seems to worry them into thinking they may die and the next year they produce like crazy. I do this in the fall.