For security, the Guest you've added must first verify ownership of the Guest email address you added. Check these three things:
- email verification
Your Guest can see whether his/her email is verified on the camio.com/me page.
- account created
If your Guest has already tried to resend the email verification and hasn't received those verification emails, then the Guest's account itself may not have been created yet.
Make sure that the Guest is currently signed-in with an account that uses the same email address that you invited as Guest.