Register in IEEE A ranked conferences - Student or full registration?
That seems clearly written to me. You aren't allowed to present a paper unless at least one of its authors has paid full registration. Maybe ethically questionable, but clear. What is your doubt? Have you read the instructions to which you were referred? Do they confirm it?

EDIT after your comment: "full registration" very likely means "IEEE member" or "non-IEEE member" (whichever applies).