item class change is not triggering new item request based on the New Item Class

Summary:

Item class was initially XYZ on the Item and the New Item Request and Definition process workflows was followed based on the set up for Item class XYZ and the NIR was completed.Now there was a change in item class from XYZ to ABC and this has to follow a different definition steps based on item class ABC. But the item is already approved as the NIR based on Item class was already completed. How do i revert or create a New NIR for the item for item class ABC

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