Sending a replacement and entering the tracking number.

[gocampingcheap]

A customer requested a return or replacement for a defective item using Ebay's returns.

We told the customer we would provide a replacement.

The customer accepted our offer.

Used the link provided on Ebays page to print a new shipping label.

After printing USPS label, I tried to mark the replacement as shipped.

Entered the new tracking number as instructed and this message popped up:

"The tracking number you have provided already exists in our system. Please use a valid tracking number for this return."

I am entering a valid tracking number and Ebay is still telling me I need to ship the replacement by June 7 or I will have to refund the buyer. 

What now?