Return Delivery re-assignment of Serial No issue

Dear Experts,

We are processing Returns from customer and able to create Return Delivery but when we are assigning/ entering Serial number, which is assigned to Customer Delivery.

I want to use the same serial number which is already used but when i am trying to use it . it shows the below screen.

We changed the status through IQ02 of equipment but still system rejecting Serial No.

Awaiting for your responses.

Thanks in advance.

Kind Regards,

PP