Multisite - Login redirecting to WPMU Dashboard Login

Having a pretty major issue....
There was an error that happened overnight... I think my database is overloaded.
When I log in to my multisite network, I'm able to get into the dashboard of the main site - When I try to login to the dashboard of any of the other sites via single sign-on, I'm redirected to a WPMU Dev Dashboard. I think somehow multisite got disabled... I have no idea how to fix this. Any help appreciated!