Or looking at the WooCommerce WC_Checkout class and code which is handling data processing and passing it to any available Gateways. I think what is needed is a plugin skip/bypass rule for the blank WooCommerce Checkout page issue since Gateways/API’s need 2 way connections.
1. Copy the code below to this BPS Root Custom Code text box: CUSTOM CODE PLUGIN/THEME SKIP/BYPASS RULES
2. Click the Save Root Custom Code button.
3. Go to the BPS Security Modes page, click the Create secure.htaccess File AutoMagic button and activate Root folder BulletProof Mode.
Note: If your WordPress installation is a subfolder installation then add your WordPress folder name in the path. Example: /My-WordPress-Folder-Name/wp-content/plugins/woocommerce/
# WooCommerce skip/bypass rule RewriteCond %{REQUEST_URI} ^/wp-content/plugins/woocommerce/ [NC] RewriteRule . - [S=13]