not able to combine orders for same buyer - Tracking number added is already used 4 different buyer

[louiesgift]

I combined 2 orders for same buyer & address in Stamps program & created ship label.  The tracking only updated to 1 of the orders in eBay. (The combine orders use to work in stamps to eBay update).   I tried to add the track # to the other order but getting error message "Tracking number added is already used for a different buyer".   Ugggh... So, voided stamps label to try to combine orders in eBay but can not find where to do so. Do not see it on my seller hub overview page.  Help, please.    

[wastingtime101]

Check the buyer IDs @louiesgift . I am guessing the IDs are different - even if just by one character - meaning the buyer could have used guest checkout and made 2 separate purchases which cannot be combined because the user IDs are different.