This issue is related to the parent sku of the variation you are trying to list on Amazon. This can be caused because parent sku is already used on Amazon catalog.
To solve this issue, you need to delete the related parent sku from the Amazon catalog and recreate it again after waiting 24 hours.
1- Select the parent SKU and go to “Three dot icon>Advanced Sync Options>Delete, Delay & Recreate”.
2- Sync the channel from the top left.