Some of the most common reasons for a magnolia tree not blooming are not enough sunlight, too much sunlight or bud damage from an early spring frost. Dry spells can also effect the ability of the plant to produce flowers, so it is important to keep the surrounding soil moist with regular watering.
One of the most important things to remember when planting a magnolia tree is to not plant it close to a wall. If the tree is close to a wall that absorbs the morning sun, it can cause the tree to heat up and begin growth prematurely. Premature growth makes the flower buds more susceptible to the cold, which can cause them to die before being able to bloom.