Why cant I invite a team member

I am an Admin in our GitLab tenant and I am trying to add one of my team to a project. However, when I fill out the form and hit the Invite button an error message pops up saying “Select members or type email address” ?

I’m not sure if I need to add the team member first somewhere else first?. Im a newbie and would appreciate any advice. Rick

I am new to Gitlab, and have issues too, but I believe that to invite a member to your project it has to be a Gitlab registered user first.