Some say you can add the same tracking for both items, have you tried this ? I have never done this so I'm sorry, not sure if it can be done.
If you cannot manually add that tracking to the other item, you can contact eBay Customer Services explain both items sent in on package with one tracking. If they won't add that tracking for the other item, you will have to wait 14 days for the payout for the second item.
If you need to, 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.
@toy.in.-46