Www not resolving OR URL forwarding

I have recently changed my ecommerce website host and changed my nameservers to use Cloudflare. I have pointed the root CNAME to host and www CNAME to host.

The root domain works fine, but www does not. Message is always, “There was a problem loading this website. Try refreshing the page.”

I have also tried the page forwarding Rule:
www-exampe-co-uk/* both 301 and 302 to htt-ps://example-co-uk/$1

(ignore the dashes in the example links above - it won’t let me put links in the post!)

I have tried the rule in combination with the www CNAME record, and also using an A record for www pointing to a dummy IP address instead.

It’s been well over 48 hours since propagation. Nothing works! Just the same “try refreshing the page message” every time. It also still has the “Shopify” icon in the tab (my old host). The domain itself was purchased through Google, and is still held with Google. Shopify have confirmed that there are no records of the www subdomain on their system. I’m at a loss what else to try!