Internal Server Error - Opencart - php

Question

I've downloaded an opencart installation in my local server in order to use it as a test and i'm not able to view the site. When i use the default htaccess file the browser returns a 500 error and when i remove the htaccess file the seo - links do not work. (404)
Any ideas?
My .htaccess file
# 1.To use URL Alias you need to be running apache with mod_rewrite enabled.
# 2. In your opencart directory rename htaccess.txt to .htaccess.
# For any support issues please visit: http://www.opencart.com
Options +FollowSymlinks
# Prevent Directoy listing
Options -Indexes
# Turn on Expires and set default to 0
ExpiresActive On
ExpiresDefault A0
# Set up caching on media files for 5 weeks
<FilesMatch "\.(flv|ico|pdf|avi|mov|ppt|doc|mp3|wmv|wav)$">
ExpiresDefault A3024000
Header append Cache-Control "public"
</FilesMatch>
# Set up caching on media files for 5 weeks
<FilesMatch "\.(gif|jpg|jpeg|png|swf)$">
ExpiresDefault A3024000
Header append Cache-Control "public"
</FilesMatch>
# Set up 1 day caching on commonly updated files
<FilesMatch "\.(xml|txt|html|js|css)$">
ExpiresDefault A86400
Header append Cache-Control "proxy-revalidate"
</FilesMatch>
# Force no caching for dynamic files
<FilesMatch "\.(php|cgi|pl|htm)$">
ExpiresActive Off
Header set Cache-Control "private, no-cache, no-store, proxy-revalidate, no-transform"
Header set Pragma "no-cache"
</FilesMatch>
<IfModule mod_deflate.c>
<filesMatch "\.(js|css|html|php)$">
SetOutputFilter DEFLATE
</filesMatch>
</IfModule>
# Prevent Direct Access to files
<FilesMatch "\.(tpl|ini|log)">
Order deny,allow
Deny from all
</FilesMatch>
# SEO URL Settings
RewriteEngine On
# If your opencart installation does not run on the main web folder make sure you folder it does run in ie. / becomes /shop/
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
RewriteRule ^sitemap.xml$ index.php?route=feed/google_sitemap [L]
RewriteRule ^googlebase.xml$ index.php?route=feed/google_base [L]
RewriteRule ^download/(.*) /index.php?route=error/not_found [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !.*\.(ico|gif|jpg|jpeg|png|js|css)
RewriteRule ^([^?]*) index.php?_route_=$1 [L,QSA]
### Additional Settings that may need to be enabled for some servers
### Uncomment the commands by removing the # sign in front of it.
### If you get an "Internal Server Error 500" after enabling any of the following settings, restore the # as this means your host doesn't allow that.
# 1. If your cart only allows you to add one item at a time, it is possible register_globals is on. This may work to disable it:
# php_flag register_globals off
# 2. If your cart has magic quotes enabled, This may work to disable it:
# php_flag magic_quotes_gpc Off
# 3. Set max upload file size. Most hosts will limit this and not allow it to be overridden but you can try
# php_value upload_max_filesize 999M
# 4. set max post size. uncomment this line if you have a lot of product options or are getting errors where forms are not saving all fields
# php_value post_max_size 999M
# 5. set max time script can take. uncomment this line if you have a lot of product options or are getting errors where forms are not saving all fields
# php_value max_execution_time 200
# 6. set max time for input to be recieved. Uncomment this line if you have a lot of product options or are getting errors where forms are not saving all fields
# php_value max_input_time 200
# 7. disable open_basedir limitations
# php_admin_value open_basedir none

Answer 1

.htaccess files in general are very sensible to syntax, and any fault can raise up a http 500 error. Faults can be linked to syntax errors and/or directives which are not supported after httpd's upgrade.
I suggested you to test step by step by making a backup copy of your .htaccess and start with blank file adding some sections until your server raise up the error.
When you have it, consider to resolve the problem by nature.

Answer 2

The first thing to do when debugging 500 Server Errors in OpenCart is to look into your server's error log and find the exact error message.
If there aren't any, you may need to enable them explicitly by adjusting the error_reporting, display_errors and log_errors settings in your PHP configuration. You can also temporarily change them in your main index.php file directly.
Once you know the exact error message, fixing it is a simple process.
We've covered some of the most common OpenCart error messages causing 500 Server Errors in our blog post: Server Errors and Blank Pages in OpenCart: Most Common Causes.
I'd recommend against trying to fix blank pages and 500 Server Errors without being able to look into the error log. These issues can be caused by pretty much anything starting from your server configuration and restrictions to broken OpenCart code so you really need to know what you're dealing with.
In your particular case, it is most likely caused by your server configuration prohibiting specific rules from being placed in the .htaccess file.