Custom Label information was never printed on the invoice. I think it is considered seller information only by eBay for some reason. Requests to print the custom label on the invoice has been in these forums since eBay Selling Manager days.
There was a way to show it by selecting print full sales record in Selling Manager but it also printed private seller notes field in the record. If you do not use the Seller Notes it may be useful. I do not know if the new Seller Hub has a similar feature. You could try it if the feature is there to see what prints. However, I believe that printing the full record took more than one sheet of paper compared to the print packing list option.
