Being able to set the "Parent Link" field in Jira DC

I want to have a hierarchy above the Epic in Jira DC.
To do this I need to set the “Parent Link” field, I have tried to accomplish this via the component Accessor, but with no success.
This is the script I have:

def usr = ComponentAccessor.getUserManager().getUserByName(“christophe.debeule@exalate.com”)
def newParentLink = syncHelper.getLocalIssueFromRemoteUrn(replica.parent.urn)?.key
def issueManager = ComponentAccessor.getIssueManager()
def customFieldManager = ComponentAccessor.getCustomFieldManager()
def parentLinkField = customFieldManager.getCustomFieldObject(10403L)
def parentLinkFieldType = parentLinkField.getCustomFieldType()

if (newParentLink) {
newParentLink = parentLinkFieldType.getSingularObjectFromString(newParentLink.toString().replaceAll(“'”,“”))
}

//def mutableIssue = issueManager.getIssueObject(issue.key)
mutableIssue.setCustomFieldValue(parentLinkField, newParentLink)
issueManager.updateIssue(usr, mutableIssue, EventDispatchOption.ISSUE_UPDATED, false)

I get the error that the issue is not found.
Any tips?

Kind regards