Unable to access admin of multisite installation

Unable to access admin of multisite installation. This problem is driving me crazy. I’m not able to get into the admin of the main site or any of the subsites. No one else is either. We had a brute force attack, so I assumed it was some level of security (have Sucuri and iThemes Security). But changing Sucuri back to defaults and iThemes off completely doesn’t change the issue.

Finally restored from a September 26th backup and the issue persists.

Has anyone seen anything like this before? Any ideas?

All the public pages are visible.