If using Simple Delivery the tracking should be added automatically.
However, recently some sellers have found this not possible, and community managers have confirmed there is a current technical issue.
Contact eBay Customer Services see if they can add the tracking for you, unfortunately without it, there is a 14 day wait for the payout to be released.
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 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@ruthnpete2011