There might be a case when you delete a product from Shopify and then recreate it with the same details. It might look like the same product to you but for systems, it will be a new product. In such cases, you can delete the request and recreate it.
Open the request using the request ID or order ID.
On the request detail page, please click on the delete button. Please note that if you have any information to capture like reason or comment from customer, please copy that and keep it somewhere.
Once deleted then click on the exchange option on the left side and click on "Create new request".
Here enter the order number and select the item you want to start for exchange then submit the request. It will create a new request for you with the correct product and you will be able to take action.