Help Center custom domain not secure

We’ve created a custom domain through SiteGround for our help centre & enforced it with SSL & HTTPS, however, the site still shows up as unsecured and gives us this error:

NET::ERR_CERT_COMMON_NAME_INVALID

We can see that the certificate is not the correct one as the common name is listed as intercom.help, but it should show up as our custom domain.

We’ve tried deleting & re-creating new SSL certificates as well as CNAMEs but nothing seems to be working to update the certificate on our help centre site. Any help would be appreciated!

Thanks.