You should be able to add the new tracking to the order by going to the Order Details > Postage > dropdown menu (beside track package) > Add Tracking > + Additional Tracking Number. Or see if there is an Edit Tracking link.
If you can't change it you can contact customer support to do it using callback on here:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
eBay will then release the payment two days after the tracking confirms delivery. Otherwise the money will be held for 14 days.
It's possible that as a new seller the money will be on hold up to 30 days anyway, regardless of the tracking.