It’s likely someone in the item’s approvals chain has sent the item back to the initiator. An item can be sent back at any time during the approvals process by whichever approver is currently reviewing the item. When that happens, the initiator can correct or clarify the item and resubmit it. The approvals process for that item then starts over from the very beginning. So although it may appear that you’re being asked to approve a duplicate of an item you’ve already approved, you are in fact approving the original item that has newly added and/or corrected information.