I just moved over my DNS records from Route 53 to Cloudflare. My site is hosted on S3. All records resolve correctly with the exception of the www cname which points to my root domain. Cloudflare simply will not resolve it. Any other combination of letters for a subdomain pointed to my root domain will resolve correctly. Digging the www record returns no result. If I assign a cname of ww instead of www, it will instantly resolve that sub domain correctly.
My other domains previously hosted on Cloudflare all work correctly with the www CNAME. The new domain will not resolve.