If one of your Custom Domains are showing a "Missing DNS Record" status (see image below), this is likely a result of either the CNAME DNS record not being properly pointed to one of the Managed Domains in your account or the entered domain name in SUPPRESS doesn't match the CNAME DNS record. OPTIZMO runs integrity checks to make sure there are no issues with your Custom Domain's CNAME DNS record.

To fix this - you will want to verify that the CNAME DNS record is pointing to one of the Managed Domains in your account and check if you have entered the correct domain name in SUPPRESS.