This article provides guidelines on how to verify why a field is NOT being copied when cloned.
Instructions
If you find yourself in a situation where a certain field is not being copied, ask yourself 2 questions:
Is the field included in the exclude fields list?
If the answer to this is YES, remove the field from the exclude fields list.
A field on the exclude fields list will not be updated and will be empty/cleared on the cloned issue.Is the field in context and on the screen?
A field value cannot be updated if it is not on screen.
If the field is not appearing on the screen, you need to add it. Follow this article for that: https://support.atlassian.com/jira-cloud-administration/docs/add-a-custom-field-to-a-screen/