Automatically login user across multisite.

I’m having a problem with my multisite. I have two subsites that have mapped subdomains, and I can’t get to them via admin.

I have set up a test site, and I have all plugins disabled, but still can’t get it to work. I am using default WP domain mapping.

In the My Sites list, if I click on the dashboard for a mapped domain, I get a login. If I put in the URL manually, I am just seeing the admin for the primary site. Please check and help.