Occasionally, grass seed won't germinate because it is old or of poor quality. Usually, the problem is a result of inadequate water or improper planting time and technique. Water the seed more frequently as your first course of action.
The best time to plant grass seed is in late summer to early fall when temperatures are cooler and the soil is moist. Grass seed planted in late fall may be killed by winter frosts, while those planted in late spring may not germinate if temperatures rise.
Grass seed needs cool, moist conditions to germinate. Plant grass seed when temperatures are cool but not cold. Cover grass seed with a 1-inch layer of straw mulch. Water the seed lightly at least daily to keep the soil moist. During dry weather, gently water it several times per day so as not to disturb the grass seed.
Although grass seed isn't buried during planting, it must make good contact with the soil. Use a lawn roller for a large area or gently brush the soil with the back edge of your rake. Even grass seed adapted for shady areas requires at least two to four hours of sunlight per day. If your grass seed was planted in deep shade, it may not germinate.