Not all buyers have that QR collection code, it's not mandatory for the seller to have this.
If the buyer has paid and collected the item, just finalise it this way:
You need to do this now, only on the Seller Hub
https://www.ebay.co.uk/sh/ovw
go to Orders >> Awaiting Postage / Print Postage label, and then click the box on the left of the item.
https://www.ebay.co.uk/sh/ord/?filter=status:AWAITING_SHIPMENT
From the Postage tab above, use the drop down menu there, if the option to mark as collected is not there, then select Mark as Paid and Mark as Dispatched.
Dispatched is eBay's wording for a collected item.