Vantage, Multisite and each site with its own first-level domain name
I installed a WP
installation from the scratch. Flawless.
I activated the Multisite feature, using subdomains. Everything worked like a charm.
Then I added some sites. Good.
And then Vantage. Good too. Everything was working as expected.
Then, I modify every site in my installation to give each site its own first-level domain so instead of having site1.mainsite.com and site2.mainsite.com, now I have site1.com and site2.com.
The front-end of all of them are working perfectly but when I try to log into any of them, I'm presented with the logon screen, I enter my credentials for every site and they are accepted. However, I'm consistently redirected to the front-end of the site I'm trying to log into (and I'm not logged in after all).
Perhaps it has something to do with the .htaccess. Can someone help me solve this please?