Is this for a ' combined invoice' for items? There is a current major issue with offering a combined invoice contact eBay Customer Services see if they can add the same number to all the items, as some members say this is possible , others say not. CS can advise if possible , and can add the tracking numbers for you.
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.
@seawatcher1066