I have the same problem on checkout page:
Warning: array_unique() expects parameter 1 to be array, null given in /home/gupcit5/public_html/store/wp-content/plugins/woocommerce/includes/gateways/cod/class-wc-gateway-cod.php on line 110
I think the reason of this problems here, in …/wp-admin/admin.php?page=wc-status
form-billing.php version 2.0.0 is out of date. The core version is 2.1.2,
…
form-shipping.php version 1.6.4 is out of date. The core version is 2.1.2,
…
single-product.php version – is out of date. The core version is 1.6.4,
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I’m sorry, but next day we plan to run our new e-commerce shop.
Please help us to fix it asap.
Thank you.
Dmitriy.