Many of the newer eBay accounts have been converted to their new horrible shipping label interface.
Older accounts are being slowly updated to the new label interface. They recently updated one of my accounts dating from 1999 to the new label system.
It is however possible to switch back to the old label system even if eBay has removed the link they used to show to change back. This possible if eBay has only hidden the old label system by default and permanently removed your ability to use it.
To switch back you only need to edit the URL for the new label and reload the resulting URL in a new browser tab.
This script will do that for you.
Open the Script Editor in Applications > Utilities
Choose File > New
Paste this script in.
Choose Export > Script (this is an editable copy)
Choose Export > Application
Place the exported Application on your desktop somewhere, such as the top corner, where you can easily double click it while using Safari.
When you go to print a label eBay will open. Browser tab pointing to the new label system.
Select and copy the URL of this tab to the clipboard.
Then double click the Application on the desktop.
It modifies and URL to point to the old label system and opens it in Safari.
You can change the script to work with another browser or the default browser.
If it does not work then eBay has disabled access in addition to hiding the old label system
get the clipboard set the clipboard to (replacement of "https://gslblui.ebay.com/gslblui/new_label" by "https://gslblui.ebay.com/gslblui/back_to_classic" for the result) on replacement of oldDelim by newDelim for sourceString set oldTIDs to text item delimiters of AppleScript set text item delimiters of AppleScript to oldDelim set strtoks to text items of sourceString set text item delimiters of AppleScript to newDelim set joinedString to strtoks as string set text item delimiters of AppleScript to oldTIDs joinedString end replacement set c to get the clipboard tell application "Safari" open location c activate end tell