If it’s not verified that means that Apple can’t see the certificate. If you navigate to https://YOUR_DOMAIN.com/.well-known/apple-developer-merchantid-domain-association does it trigger a download of the certificate? 
If it’s not verified that means that Apple can’t see the certificate. If you navigate to https://YOUR_DOMAIN.com/.well-known/apple-developer-merchantid-domain-association does it trigger a download of the certificate?