Adx problem

I'm experiencing an issue with Adx that is causing a low fill rate and I'm open to suggestions as to how to address the problem. I'm looking for help to resolve this issue immediately or at least within the week. If you have experience with Adx and can provide solutions to this issue, please apply and let me know how you can help. and i have google ad manager adx i am facing one problem unfilled and Default Ads most unfilled coming on this and i cant even inactive this i just need you to inactive Default its only showing in Invetory Rules