The Browser is reporting a false positive... The issue actually relates to the "Minimum TLS Version", if your banner server support TLS 1.0 this deprecated in modern browsers and will report as not secure appearing as content was included over http as opposed to https.
Having spent sometime with this issue I can confirm I was able to resolve the problem.
In the first instance I updated the URL for fl.js to it's full https url via Banner Delivery Settings > Delivery File Names:
Flash Include (Can be a full URL)
With the above in place we changed the minimum TLS supported by the server to TLS 1.1
This resolved the mixed content warning.
Hope this helps someone.
Thanks Laurie
