Your tree has/had allopathic properties.

Advice: remove the root ball.

Norway maples are only slightly allelopathic....as are the vast majority of other trees. And much of the allelopathic properties are reduced or eliminated once the tree is cut down.

Unless the stump grindings were completely removed from the planting area, they could be the reason the lawn is not growing well. Any wood based product - sawdust, stump grindings, wood chips, bark mulch, etc. - when mixed with the soil will tie up nitrogen availability as they decompose. And lawns need a lot of N!!

If you try again after a good application of an N based fertilizer (like urea), the turf grass should do much better