Website defaced after change in . htaccess

Question

I developed a website, but went to .htaccess of the project to apply a rule to force the HTTPS on the page (For exploratory purposes only, I would not apply this way.). See below the implemented rule:

<IfModule mod_rewrite.c>
    RewriteEngine on
    RewriteCond %{HTTP:X-Forwarded-Proto} !https
    RewriteCond %{HTTPS} off
    RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME}\.php -f
    RewriteRule ^(.*)$ $1.php
    RewriteCond %{REQUEST_FILENAME}\.html -f
    RewriteRule ^(.*)$ $1.html
</IfModule>

It turns out, after doing this, my site redirected normally (I’m using the Browser-Sync for auto-refresh), but then it completely disfigured. If you inspect the code, it is perfect. In the Devtools of the browser it shows no error (or no error relevant to the problem in question - it is worth noting that in some refresh, the console shows some Warning).

You can see the site here: brengenharia.com.br

What I’ve tried to solve the problem:

• Check for errors in Devtools [Status-free];
• The rule of .htaccess has already been removed but the disfigurement remains [Not solved];
• Apply reverse rule (Force HTTP) [Did not resolve];
• Identify open tags in HTML [Did not resolve];
• Trying to clear cache or accessing anonymous browser [Did not resolve];

Well, that’s it. I really need your help. Tell me if you’ve ever had a similar situation, how you solved it or how you would solve it, where you would check to try to solve it.