If the orders are not completing automatically, There could be two reasons
- You did not select Virtual while creating the product.
- WooCommerce is not receiving response from the payment processor.
If the plugin is not receiving the expected response that the payment is completed, then the order status will not be updated.
Please consult your payment service provider if they support the eCommerce plugin you are using.
In the case of online bank transfer, the same process is also expected. If the bank does not provide a response after completing the payment back to your site, then the order will not be marked complete automatically.