Post office query

[mizu]

Posting here for traffic so apologies for the boring post but I don't know what to do.
Sold something on eBay last week, posted the next day to be guaranteed for the next day.
Get an email 2 days later saying the person I sent it to hadn't received it.

Go onto the track and trace PO website and type in the ref number and get this message:

"We were unable to deliver this item as the recipient refused to accept it. It will now be forwarded to our National Returns Centre to determine sender's details".

Emailed the woman who should have received the parcel who replied that she had chosen a delivery point from the drop down menu and had picked parcels up from there before, a newsagent.

Last update on PO website is that the parcel has been delivered to PO Box by National Returns Centre.

What does this mean? Back to the post office I posted it from, perhaps?

Can anyone enlighten me as to what to do next?

My DD was the recipient and in a similar case, it went back to the PO that it was sent from for the sender to get it.

If it's not there, it'll be your local sorting office.

Thank you for the reply. Makes sense, I will go in search for it - when I have time!