Problem using LeadPages for Landing Pages and adding to Sitemap.xml

jessential

I am seeking to use LeadPages for Landing Pages for a client and cannot seem to correctly add them to the Sitemap.xml in the Google Search Console.

They are visible in the web host's CPanel version of the sitemap.xml and have been indexed in the Fetch as Google in the Google Search Console. Yet they will not show up in any sitmap.xml test within the Google Search Console.

Does this have something to do with the pages being added through LeadPages WordPress plugin? How can I get them to be added to the sitemap.xml in the Google Search Console?

Example pages:

http://ddinstruments.com/expello-electronic-drain-valve-mn

http://ddinstruments.com/chevy-gauge-cluster-repair

http://ddinstruments.com/remanufactured-international-instrument-clusters

http://ddinstruments.com/kenworth-truck-speedometer-repair