Connector to Jira Costum Fields

[Julls]

Dear All,
I'm having problems to synchronize Polarion Fields (Drop Down) to Jira Costum Fields. I'm always getting this error:
2019-04-15 10:23:45,092 [Worker-0 | u:j****n.j*******r | job: synchronizer] ERROR root - Could not update 'POLIMP-727' on 'JIRA-Jira Test Julian':null
Failed to update fields: {customfield_14006=[Field [Customer (single choice)] not updated - Not on screen or unknown.]}

I attached the XML of the Jira Comstum Field.

Do you know any solution to this Problem?

Thank you already!