You’re on the right track! To sync the Jira Created Date to a custom field in Azure DevOps, your approach is almost correct, but let’s clarify the setup and double-check a few things.
Possibly there is a mismatch for the date format coming from Jira. Can you try the following:
// Place import at the top of the ADO Incoming Script
import java.text.SimpleDateFormat
// Only process if replica.created exists
if (replica.created) {
def formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
def formattedDate = formatter.format(replica.created)
workItem.customFields."JiraCreatedDate" = formattedDate
}