Here are the steps to resolve HTTP Error 500 Internal Server on WordPress.
Method 1 Clear Browser Cookies and Cache
Please make sure that this error is not caused by your browser. The problem may not be with your hosting server or WordPress website, but with the browser you're using. For this reason, you can first clear your browser's cookies and cache.
How to Restore Default WordPress .htaccess File
A changed .htaccess file can cause errors. This file is used for the server configuration process. The server will search and execute the .htaccess file when the website is loaded by visitors.
1. Login to cpanel
2. Then go to the File Manager menu. Please enter the public_html directory. Then, click the Settings button in the upper right corner.
3. The Preferences pop-up window will appear on the screen. The .htaccess file is actually located in the public_html directory. However, it is hidden by default. You need to display the file by checking the Show Hidden Files (dotfiles) checkbox. Then, click the Save button to save the settings.
4. The .htaccess file is now visible in the public_html directory. Right-click the .htaccess file and you will see a series of settings menu. Select Edit to edit the contents of the file.
5. A confirmation pop-up window will be displayed. The window contains information that you will be editing the .htaccess file. Click the Edit button to continue.
6. Here are the code lines of the .htaccess file by default based on the WordPress documentation.
# BEGIN WordPress
RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
# END WordPress
Copy and paste the line of code above into your .htaccess file. Click the Save Changes button to save the file changes.
9. Congratulations, you've successfully saved your .htaccess file. This file is required for WordPress websites to be accessible. Try visiting your website to make sure this fixes the 500 error.
Method 3 Temporarily disable plugins
Active plugins can cause errors on WordPress websites. To make sure the error isn't caused by a plugin, temporarily disable the plugin. Follow these steps.
1. Login to cpanel
2. Then go to the File Manager menu. Enter the public_html/wp-content directory. Several directories will be displayed. Right-click the plugins directory and a row of settings menu will appear. Select Rename to change the directory name.
3. The Rename pop-up appears to change the directory name. Change the directory name to plugins.deactivate and click Rename File to save the changes.
4. You've successfully changed the directory name and deactivated all WordPress plugins. Then, try accessing your website. If it's accessible, one of your plugins is causing the error.
5. To find the problematic plugin, rename the plugins.deactivate directory to plugins.
6. From here, you can deactivate the plugins one by one by going to the public_html/wp-content/plugins directory. Then, rename the plugin directory to name.deactivate. Example: litespeed-cache.deactivate
Try accessing your website again. Repeat step 8 until you find the plugin that is causing the error.
How to Restore Default PHP Selector
Some settings in the PHP Selector may have been accidentally changed. You can go to the Select PHP Version menu through cPanel. Then, click the Reset to default button on the right.