Reorder.Item must be child of Reorder.Group
You're attempting to render a <Reorder.Item> component.
<Reorder.Item />
You're receiving a message that Reorder.Item must be a child of Reorder.Group. This means you either haven't rendered a Reorder.Group, or you've rendered Reorder.Item outside of your Reorder.Group.
Solution
Ensure any Reorder.Item component is rendered somewhere within a Reorder.Group component:
<Reorder.Group>
<Reorder.Item />
</Reorder.Group>
It doesn't need to be a direct child. This is also okay:
<Reorder.Group>
<div>
<Reorder.Item />
<Reorder.Item />
<Reorder.Item />
</div>
</Reorder.Group>