A misbehaving .htaccess breaks every request, is never read, loops, or works until something later undoes it. Read the response (curl 3,008 -I) and the error log, and ask four questions in order: is the request reaching this site (apache2ctl -S, Virtual Hosts)? Is the file read (Ignored Rules)? Does it parse (Finding a 500 Error)? What do the rules do (rewrite:trace, Rewrite Tracing)? The test site listens on port 8111 with DocumentRoot /var/www/example and the error log /var/log/apache2/example-error.log, and has mod_rewrite and mod_headers enabled but not mod_expires.