Multisites w/sub-domains was working

I have two sites that were set up for multisites that were working.

There were no sub-domains active but they WERE created.

Now, I've gone back to them to get started, and tried to create a new site on both of them.

There appears to have been some error, or problem, but it shows up in the Sites list??? Then I try to visit the site, but it's not there?

I made sure that registration was not disabled. What else should I be checking?

Tom