Woocommerce checkout page internal server error

A most popular problem of 500 internal server error is some fatal errors in backend part of your website. To find, where you got problem, you should to remove this from your wp-config.php file:

define( 'WP_DEBUG', false );

And instead of it add this code:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

The next step will be to go to the page of your website, where you're getting 500 internal server error. After open this file {your-website-folder}/wp-content/debug.log. Here you'll find all errors, which caused php files. There you'll find Fatal Error: {why it occured and where} .

So, after this steps you'll have to open new question about your error.

You may want to check your outgoing Wordpress Mail Services and disable any plugin associated with sending out order completion emails. This is what worked for me. I was sending our order completion mails using Mailster and connected to AmazonSES SMTP. So I disabled the AmazonSES plugin and everything worked fine. I had recently updated the AmazonSES plugin and I am thinking the update broke it.