Error: 'X-Frame-Options' to 'SAMEORIGIN'.

You remove that with this hook:

remove_action( 'template_redirect', 'wc_send_frame_options_header' );

From /woocommerce/includes/wc-template-functions.php

/**
 * When loading sensitive checkout or account pages, send a HTTP header to limit rendering of pages to same origin iframes for security reasons.
 *
 * Can be disabled with: remove_action( 'template_redirect', 'wc_send_frame_options_header' );
 *
 * @since  2.3.10
 */
function wc_send_frame_options_header() {
	if ( is_checkout() || is_account_page() ) {
		send_frame_options_header();
	}
}
add_action( 'template_redirect', 'wc_send_frame_options_header' );

@ignitemedia, I’m sorry I never replied. Somehow I didn’t see this post.

@matt Thiessen, thanks for providing that info!

it doesn’t work for me, I added
remove_action( ‘template_redirect’, ‘wc_send_frame_options_header’ );
inside functions.php of my template
any idea?

Your code might be running too late if you put it in your theme, try creating a new file: wp-content/mu-plugins/somefile.php and add your code there.