10 reasons why Peonies do not flower:

1. The plant is planted too deep or too shallow
2. The plant is getting too much fertilizer with Nitrogen
3. The plant in under or overnourished ; Peonies thrive with limited care and fertilizers.
4. Buds were were killed by a late frost, disease or excessive heat
5. Not enough sunlight to produce flowers
6. The plant is too young or immature
7. The plant is overgrown or overcrowded
8. The plant has been moved or divided too often
9. The foliage was cut back before the leaves turned brown
10. The soil is too wet or too dry