Why is there a www? And do you have DNS records for that? Your DNS check example doesn’t include www in the host name. Perhaps your origin is misconfigured and is improperly redirecting to www?
You will either need a DNS record for www.boutique pointing to your server, or you will need to remove the redirect from boutique to www.boutique and serve the site without the www.
Note: If you add the DNS record for www.boutique, then unless you have a dedicated certificate from Cloudflare, then Cloudflare’s SSL will not work - you would have to set that subdomain to and bypass Cloudflare services.