Multi-domains – add a new site to root

Hello,

I’m running a multisite on example1.com, and I have a few sites running underneath this domain (*.example1.com). I have added a new domain, example2.com, but when trying to create a new site without a subdomain (I want to create it at the root domain), I get ‘invalid name’.

How can I create a site running on example2.com ?

Thanks