You can resend an invite by going to the card or Admin details and clicking the Resend invite link.
If the Resend invite link is not available, this means that the invite has been accepted (e.g. the invite link was clicked). If this is the case, the invitee can simply go to the Login page and request a new password.
If you've resent the invite, but the recipient still hasn't received it:
- Verify with the person that the email address you entered is the email account that they are checking
- Check that the email address entered wasn't accidentally miskeyed
- Ask the invitee to check the spam folder of their email account