Multisite: subsite not loading css of theme

Hi everyone,

I have, for the first time ever, successfully created a multisite using the domain mapping plugin. However, when I create a subsite, it doesn't load the css of the (default) theme.

I read on the forums that I should force httpS, but I was also told not to do that by a service agent of WPMU. Now I'm not sure what to do...

Support Access is hereby granted.

Thanks !