Call Diagnostics Enabled: Enabled Only When CDR Enabled Flag is True
It sounds you may have done this. What may be tripping you up is that the CDR Enabled Flag service parameter values are not a cluster wide parameter and you must configure each Communications Manager node individually . You only need to enable this flag on CUCM nodes which run the Call Manager service (aka call processing nodes).
So, under Service Parameters, go to the Call Manager service on each CUCM node in your cluster and toggle CDR Enabled Flag.