Adding Designer - Am I restricted?

[MeacieFairfax]

I am trying to add a designer to help me create a course, and it says the user does not exist. Which is true. However, I cannot add; do I have to add another way? Talk to the administrator.  How do I find out who is the administrator? 

[Gabriel33 · Accepted solution]

Are you using a Free for Teachers course? There were some issues with adding students a couple of weeks ago in that platform, seems it could be fixed by adding the invitee's email as a "Login ID" instead of an "Email Address".

See, for example, this post: Solved: "We were unable to find matches below" error when ... - Instructure Community - 636716