While these issues are not common, they can occur on budget hosts or hosts that may not be properly configured for the installer to run.Below is a list of “QUICK OPTIONS” and “ERROR RESPONSES” and recommendations for each. For error codes please jump directly to that code number.

QUICK OPTIONS

Timeout Issues
The web server is not configured to run long enough to extract the archive and install the database.

• The quick & easy workaround is to perform a manual extraction.
• Its also recommended to use mysqldump for larger databases and shell_exec for large archives if possible and your host supports them.

Disable Plugins
If you have security or caching plugins installed its recommended to temporarily disable them to avoid conflicts at install time. Some securityplugins can reach outside of a WordPress and monitor external folders, while others once enabled in a new environment need additional configuration.

• During Build: This can be done by creating your package with all cache and security plugins temporarily disabled and add all cache paths to the directory filters list.
• Before Install:If you’re already too far into the install process and don’t want to create a new package you can alwaysperform a manual extraction and temporarily remove or rename the plugin folder of the plugin yoususpect to be causing issues. Finish up the install process and then restore the plugin.
• During Install: On Step 3 of the installer under options is a select box where you can disable plugins. Check the option to disable all plugins and continue with the install.Once you have the site installed you can then re-activate all the plugins.

Wordfence Plugin
Wordfence is an excellent plugin, but moving a WP site with it enabled can cause issues when initially trying to get the site re-deployed.

• The quickest fix is to disable the plugins firewalltemporarily until you get your site deployed.
• Wordfence has a firewall feature that filters php code. So when running the installer.php, it could be blocked by Wordfence.This is more relevant for users with multiple WordPress installations. For example if you’re attempting to duplicate a WordPress install while anotherWordPress site existed in another directory, then you may get an “403 Access Denied” error since Wordfence works across multiple directories.Below are some the steps to whitelist the installer:
  1. Go to your Wordfence Live Traffic page.
  2. Look for a red highlighted section saying installer.php was blocked. Click the “Whitelist param from Firewall” button and see if the installer.php works.
  3. After installation if you remove the rule, but be sure to white list it again when you go to run the installer.

Check .htaccess file
Improper web server configurations can cause issues such as:

• Missing directory Index: To fix add DirectoryIndex index.html index.php to .htaccess
• Check with your host for mod_security rules for example the following rule on Siteground hosting will lifta server security rule for the installer to properly:
  <IfModule mod_security.c>SecFilterRemove 001838</IfModule>

ERROR RESPONSES

• 500 Internal Server Error
  If you get this error from any log or response please see:
  “How do I handle ‘Internal Server 500’ messages?”
• 403 Forbidden/Access Denied
  If you get this response it can be related to permissions, below are a few options:
  • Give your root WordPress folder permissions (such as 755)
    Note: Step 1 Advanced options will allow you to recursively set permissions on directories or files
  • Contact your host with the error and ask them about any firewall rules they enforce.
  • Check the .htaccess file see “Check .htaccess file” above…
  • Temporarily disable any firewall/security plugin see “Disable Plugins & Wordfence Plugin” above…

Also See:
How do I handle “Internal Server 500” messages?
Wordfence documentation
ModSecurity Site | ModSecurity Reference
Recommended hosting providers for Duplicator?