There have been issues some have experienced, with the sending of messages.
Contact eBay Customer Services, explaining your collection item has been paid for and messages are blocked from being sent with the important contact / address details.
As a reminder, when this has been settled, along with your contact details in that message, remind the buyer to bring along the 6 digit QR code and that the item cannot be released with this code. It's your only proof when scanned or numbers entered manually, that the item has been collected.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open between 8 a.m. to 10 p.m. on weekdays.
9 a.m. to 6 p.m. on weekends.
I recommend contacting CS very first thing in the morning, when the lines first open, as there's more chance of Dublin answering.
@roboxyz