To view and manage invitations to your hub, go to the settings section of your hub and select Invitations from the left hand navigation. Note: You will need to be an administrator to access this feature.
The network invitations section allows you to see all outstanding invitations that have not yet been accepted. Invites can be sent from this section or they may have been sent from individual channels.
From this screen you can cancel invitations (the link in their email will no longer work) or resend an invitation. You can also invite new members by clicking on the invite new members link.