Invite user again
Perhaps the person you invited has not responded to the invitation, or perhaps the email has been deleted by mistake. Don't worry, you can re-invite the user by following this steps:
Go to users.
On the right side of each user there is a 3 dot symbol, click on this symbol and in the menu that appears select Invite again
A new invitation will be sent to the e-mail that is connected to this spesific user.