It’s likely that stump residue is the cause of your difficulty growing grass. Sawdust and woodchips are what remain of the ground stump, and these rob the soil of nitrogen, an essential nutrient for growing healthy grass. They need to be thoroughly removed. You can first dig out the topsoil that was placed on the ground stump and set it aside, keeping it apart from the stump residue. Then remove most of the ground up chips and sawdust, which you can use for mulch in another part of the yard. Fill in the cavity with the topsoil you removed plus any additional dirt that is needed. Then apply a mixture of slow release and quick release nitrogen-rich fertilizers to give the soil a boost right away and help maintain nitrogen levels in the future. Rake the area to distribute the fertilizer evenly. Sow your grass seed, water regularly, and you should see healthy grass growing in that area.

Good luck with your project.