I was making test drives to the new system and i encoutered a problem

This is what i did: 1.new sale order 2.confimed sale order 3.view the delivery order 4.delivered the order 5.but then i returned the products and selected that the order must be refunded 6.i recieved the products 7.i created the refund invoice 8.registered the payment.

now the problem is that in sales order keeps saying sale to invoice and i cant make the invoice anymore from the sales order