I just notice that my domain doesn't work with the www prefix. I thought when customer entered the address with the www, they were redirect to the main domain without the www, but it doesn't work. In the admin, the domain with the www status is ''setup in progress''. What do I need to do to get it working?
It's all documented here: https://help.shopify.com/manual/domains/connecting-existing-domains/setting-up-your-domain