You can Invite Users from both Groups and the Global Settings Page.
As an invited user I am stuck in onboarding or my organization looks off.
Ask the sender / admin of the Archera org If you see an invite has been sent in the settings page.
Did you send the invite to an alias or their primary account?
If so, resend the invite or invite a user with their primary email.
If a user trys to sign in with another email they will not be linked to the account. Let us know if they setup a wrong account and we can remove it.