I'm running on prestashop 1.6 and i have the following error...
Mixed Content: The page at 'https://nnn.pt/pt/' was loaded over HTTPS, but requested an insecure stylesheet 'http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css'. This request has been blocked; the content must be served over HTTPS. In my header.tpl i cannot find this :(
I figured out that the E-goi module was calling Bootstrap through HTTP.