Failure to bloom is usually caused by two things: improper planting and/or insufficient light. When planting peonies, make sure to plant the eyes (the point at which new growth emerges) no more than two inches deep. Also make sure your plants get plenty of sun — 6 or more hours a day. If they're planted in a shady site, they will not flower well — if at all.
Also note that newly planted peonies usually don't flower the first year, which is spent developing a good root system and foliage. By the second spring after planting, you should see your first blooms.