Why is a user grayed out in the ColorProof GO admin overview?

If a user is grayed out in the overview, like in the example below, it means that the invitation has been sent, but the user did not click on the button in the email. This account is not yet paired to the system.

The user should complete​ the pairing. Please ask him/her to click the "Join ColorProof GO" button in the invitation email. If he/she does not have the email anymore, please send a new invitation.