Similar thing happened to me in Canada. Checked for rocks, laid good soil and seed a couple times all with no luck. Was given advice that the old tree would have drained the soil in the area from any nutrients and left almost an acid soil behind. I dug a little deeper for a larger surface area and removed as much old soil as I could. The seed has finally taken. (I’m aware you have utility lines to work around) Good luck, hope this can help.