Our yard will not grow grass ! I don’t know what has happened

https://www.thisoldhouse.com/ideas/everything-you-need-to-know-to-grow-lush-lawn

Do you have grubs? Maybe you should have the soil tested for a start.

Root rot, mole crickets possibly. Have trees grown big over it?

If your lawn isn’t growing, check its levels of sunlight, food and water, then review your mowing practices. If you can identify the problem then fixing it is easy. Check to see If you mow the lawn too short, have too much shade or too many dogs. There are sprays to spay seed on your lawn, which I find to work best to re-grow grass.

A good place to start is to take a small sample of your soil to your local nursery so they can rule out grubs and nutrient issues- best of luck :)

thank you all

So that could be a combination of roots taking up grass area and nutrients and or not enough sun.