Secure landing page issue
We have a landing page - our first landing page. When I view the link in different browsers, as well as mobile, I see that it's secure. However, when I test the link with other people, they get the message that the page is not secure and they are not able to see the landing page. I've checked the images and links and updated them all to be https, and then unapproved and reapproved the landing page. Even deactivated and reactivated the smart campaign.
Is there something else that I'm missing? Why can I see the secure page but nobody else?