It could be that apache rewrite is not enabled in your server. Run this through SSH to enable it:
a2enmod rewrite
Then restart Apache Service:
service apache2 restart
If this doesn't help, it could be that your server is not allowing your htaccess file. To solve this, edit this file: /etc/apache2/sites-available/default.
Look for:
<Directory /var/www/>
Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all
# Uncomment this directive is you want to see apache2's
# default start page (in /apache2-default) when you go to /
#RedirectMatch ^/$ /apache2-default/
</Directory>
Change:
AllowOverride None
To:
AllowOverride All
Then restart Apache again.
Also, I have had this issue once where apache user (www-data) was not given permission on that particular site. Just an extra hint.
Hope this helps!
RewriteBaseappropriately. - Callidior