When I try to "Add new User" nothing happens

Hi,

I am using a brandnew wordpress multisite. When I try to “Add new User” nothing happens (I tried in the network and on each site).
I click “Skip Confirmation Email” because I don’t want the new Users to know, that I’m working on the site until it’s ready.

I will be glad if you assist me how to do this. Please explain in dummies-mode, because I’m no native speaker.

Thank you.