Woocommerce Checkout Problem

Hello,
I was using my website with no ssl and everything was fine.But 5 days ago i buy static ip and ssl then my checkout starting internal server error. My logs:

2018-10-13T23:58:05+00:00 CRiTiCAL Uncaught Error: Class ‘WC_Order_Item_Product’ not found in /public_html/wp-content/plugins/woocommerce/includes/class-wc-checkout.php:376
Stack trace:
#0 public_html/wp-content/plugins/woocommerce/includes/class-wc-checkout.php(339): WC_Checkout->create_order_line_items(Object(WC_Order), Object(WC_Cart))
#1 public_html/wp-content/plugins/woocommerce/includes/class-wc-checkout.php(1030): WC_Checkout->create_order(Array)
#2 public_html/wp-content/plugins/woocommerce/includes/class-wc-ajax.php(435): WC_Checkout->process_checkout()
#3 public_html/wp-includes/class-wp-hook.php(286): WC_AJAX::checkout(”)
#4 public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(”, Array)
#5 public_html/wp-includes/plugin.php(453): WP_Hook->do_action(Array)
#6 public_html/wp-content/plugins/woocommerce/includes/class-wc-ajax.php(78): do_action(‘wc_ajax_checkou…’)
#7 public_html/wp-

how can i solve this problem. I complete delete and install my webside. Add just woocommerce plugin. You can try checkout, when you click checkout you will see error.
http://www.sadullahoglu.com

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