[Symfony 4] Chargement incomplet du CSS

A mon avis le .htaccess n'est pas correct. Tu mets une "RewriteEngine" on en dehors IfModule mod_rewrite.c qui comporte déjà ceci. Pour le coup tu souhaites faire une redirections vers https ?

Voici un l'htaccess par défaut de symfony avec la'jout d'une redirection HTTPS

# Use the front controller as index file. It serves as a fallback solution when
# every other rewrite/redirect fails (e.g. in an aliased environment without
# mod_rewrite). Additionally, this reduces the matching process for the
# start page (path "/") because otherwise Apache will apply the rewriting rules
# to each configured DirectoryIndex file (e.g. index.php, index.html, index.pl).
DirectoryIndex index.php

# By default, Apache does not evaluate symbolic links if you did not enable this
# feature in your server configuration. Uncomment the following line if you
# install assets as symlinks or if you experience problems related to symlinks
# when compiling LESS/Sass/CoffeScript assets.
# Options FollowSymlinks

# Disabling MultiViews prevents unwanted negotiation, e.g. "/index" should not resolve
# to the front controller "/index.php" but be rewritten to "/index.php/index".
<IfModule mod_negotiation.c>
    Options -MultiViews
</IfModule>

<IfModule mod_rewrite.c>
    RewriteEngine On

    RewriteCond %{HTTP:X-Forwarded-Proto} !https
    RewriteCond %{HTTPS} !on
    RewriteCond %{REQUEST_SCHEME} !https
    RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

    # Determine the RewriteBase automatically and set it as environment variable.
    # If you are using Apache aliases to do mass virtual hosting or installed the
    # project in a subdirectory, the base path will be prepended to allow proper
    # resolution of the index.php file and to redirect to the correct URI. It will
    # work in environments without path prefix as well, providing a safe, one-size
    # fits all solution. But as you do not need it in this case, you can comment
    # the following 2 lines to eliminate the overhead.
    RewriteCond %{REQUEST_URI}::$1 ^(/.+)/(.*)::\2$
    RewriteRule ^(.*) - [E=BASE:%1]

    # Sets the HTTP_AUTHORIZATION header removed by Apache
    RewriteCond %{HTTP:Authorization} .
    RewriteRule ^ - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]

    # Redirect to URI without front controller to prevent duplicate content
    # (with and without `/index.php`). Only do this redirect on the initial
    # rewrite by Apache and not on subsequent cycles. Otherwise we would get an
    # endless redirect loop (request -> rewrite to front controller ->
    # redirect -> request -> ...).
    # So in case you get a "too many redirects" error or you always get redirected
    # to the start page because your Apache does not expose the REDIRECT_STATUS
    # environment variable, you have 2 choices:
    # - disable this feature by commenting the following 2 lines or
    # - use Apache >= 2.3.9 and replace all L flags by END flags and remove the
    #   following RewriteCond (best solution)
    RewriteCond %{ENV:REDIRECT_STATUS} ^$
    RewriteRule ^index\.php(?:/(.*)|$) %{ENV:BASE}/$1 [R=301,L]

    # If the requested filename exists, simply serve it.
    # We only want to let Apache serve files and not directories.
    RewriteCond %{REQUEST_FILENAME} -f
    RewriteRule ^ - [L]

    # Rewrite all other queries to the front controller.
    RewriteRule ^ %{ENV:BASE}/index.php [L]
</IfModule>

<IfModule !mod_rewrite.c>
    <IfModule mod_alias.c>
        # When mod_rewrite is not available, we instruct a temporary redirect of
        # the start page to the front controller explicitly so that the website
        # and the generated links can still be used.
        RedirectMatch 307 ^/$ /index.php/
        # RedirectTemp cannot be used instead
    </IfModule>
</IfModule>