Mixed content – request has been blocked: the content must be served over HTTPS

Hello,

I have a valid certificate on the site (Acitve24). In the settings I have Redirect to HTTPS: Enabled and deals with mixed content. Still, it won’t help. Automatic redirection to HTTPS works, but the request to view a PDF file (which has HTTP) is always blocked.

On web hosting support, they wrote me to add this code to .htaccess.

RewriteEngine On

RewriteCond %{HTTPS} !on

RewriteCond %{HTTP:X-Forwarded-Proto} !=https

RewriteRule ^.*$ https://%{HTTP_HOST}%{REQUEST_URI} [L,QSA,NE]

Header set Content-Security-Policy "upgrade-insecure-requests;"

The code was already in this file, so I copied it to the beginning, but it had no effect.

They also told me that they would send it to specialists who understood more and it would not be until next week at the earliest.

However, I hope he will advise me, because I have no idea how to solve it.

The paradox is also that it works in Firefox (but not in another browser)

That’s why I want to ask for help, please.

Thank you

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