dm-sso-endpoint loading over http on ssl domain mapped subsite

I have a site in a multisite network (https://www.*****.org) that has an SSL cert, but there's a domain mapping script that is loading over HTTP: http://team******.com/dm-sso-endpoint/1511284989/?dm_action=domainmap-setup-cdsso

It doesn't look like this does anything, it just hits an endpoint, and there is no response. We don't have SSL on the main site.
Ideally the script URL should be /dm-sso-endpoint/1511284989/?dm_action=domainmap-setup-cdsso

No domain or protocol

Or, it should use the same domain and protocol as the site that it's being loaded on.

This site uses the domain mapping plugin

Mainsite URL: http://team******.com