Zendesk SLA metrics missing in Genesys Cloud CX Analytics

Can anyone clarify why our Zendesk SLA breach data isn’t populating in the Genesys Cloud CX Analytics dashboard? We migrated ticket timestamps to interaction metadata, but the ‘Time to Resolution’ report shows null values for legacy tickets.

“Custom metrics require explicit mapping during data ingestion.”

We followed the migration guide for digital channels. Is there a specific API call needed to backfill this data? Using standard Admin view.