This domain points to a 3rd party service. You likely need to configure that 3rd party service to accept the new subdomain you want to point to it. That would be done at that service provider.
A CNAME does not create a redirect. It makes an alias. To redirect, create a redirect rule, and delete the communityCNAME. Use a proxied AAAA record set to the discard prefix address 100:: for that name instead.