When you attempt to customize your site via Appearance → Customize, you get an Internal Server Error (HTTP 500 range) in the Customizer preview or the customizer redirects to this error page in the browser.

This is sometimes caused by plugin conflicts but is usually a server configuration issue.

1. Ensure WordPress, Layers and all plugins are updated. If your  premium plugins do not have an auto-update feature, you will need to check your account on the Layers website or CodeCanyon to download an updated copy to reinstall it.
2. If you are using a Layers Child Theme, deactivate it and activate the main Layers theme, then retest the customizer. If this solves it, your child theme may be causing the problem.
3. Ensure Layers is installed in the correct folder.
4. Go to Settings → Permalinks and ensure Post Name is selected, then click Save to regenerate all links, then test again.
   • If the error still occurs, go back to Settings → Permalinks and choose Default, then test again. If this works, skip to Step 6
   • If changing/resaving permalinks does not work, continue:
5. Go to Plugins and deactivate all plugins*. If you have caching plugins, clear the cache first before deactivating.
   • *The following plugins can stay active and have been cleared as the cause of this problem:
     • Layers Pro
     • StoreKit
     • WooCommerce
6. Try the customizer again from Appearance → Customize.
   • If this works, click around your menu to visit other Layers pages and ensure they work. You will need to reactivate plugins one at a time and test after each until you find the one causing the problem
   • If the error reoccurs, it is probably not a plugin issue. Continue:

The following require some understanding of FTP or how your web space is setup. If you are not comfortable working with your server config, we recommend you contact your web host to let them know you get an internal server error when trying to use the WordPress customizer and would like help troubleshooting your ,htaccess and PHP configuration.

Check .htaccess

This file controls some aspects of security on your site, and how redirects work, including permalinks in WordPress. Some security plugins will modify this incorrectly or in too strict a manner which causes problems in WordPress. Your host may also enforce specific .htaccess rules that cause problems in WordPress.

1. Single installs: Connect to your server using an FTP client and delete the .htaccess file.
2. WordPress Multisite: Visit Network Admin → Network Setup and verify your wp-config and .htaccess are configured as outlined on that page.
3. Test again and see if the problem is resolved. If so, go to Settings Permalinks, ensure Post Name is selected and re-save.
   • If turning on permalinks breaks customizing again, contact your host to troubleshoot. For best results, be sure to host your site on a host that offers WordPress hosting, or uses Linux servers.

Check PHP & Caching

1. PHP should be at 5.4 to 5.6. 5.7 is in beta and should not be used on a live site.
2. Disable eaccelerator for PHP. See this article for help or ask your host.
3. Turn off other server-side caching –  In most cases, it is better to manage caching from WordPress with a plugin designed for WordPress. unless you are on Managed WP hosting. Your host can assist you with disabling server caching such as Varnish, Pagespeed, X-Cache or Cloudflare etc – usually there is a setting in your domain page on your cPanel to turn these off.

• Troubleshooting Customizer Errors & Performance
• How to Troubleshoot Errors and Common Problems in WordPress