What type of grass do you have & what it the temperature where you live? Grass seed that is planted in soil temperatures below 50 degrees just will not grow potentially for many weeks if it does not want to. Usually for the soil temperatures to reach 50 degrees you need 7-10 days of air temperatures to reach 60+ degrees. When it is warm enough, Ryegrass is the quickest species of grass to germinate. In the correct conditions, ryegrass can germinate in 5-7 days, usually 10-14 days if it is not too cold. Hope that helps!
Grass (like other plants) needs dirt, food, water, sunshine, and warmth. My problem is it grows too quickly. If you can't get it to grow from seed, you might try sod. Check with your local nursery to see what works in your area and conditions.
If it is sparse, re-seed over top and then keep watered. You can use a lawn fertilizer at the same time and rake both the seed and the fertilizer into the soil. Keep it moist until it germinates and purchase seed that the birds cannot eat.
There are all kinds of things out there. Ask questions at a hardware store where they sell that stuff. There are things to sprinkle and there is sod that comes in squares.
Where do you live Cheryl? Any trees?