I'm having the same issue on J3.6.2 and Gantry 5.3.5
Mixed Content: The page at '
www.eazycollect.co.uk/
' was loaded over HTTPS, but requested an insecure font 'gantry-theme://fonts/roboto/roboto_bold/roboto-bold-webfont.woff2'. This request has been blocked; the content must be served over HTTPS.