eBay recommends using the latest version of certain browsers, but not every user keeps their operating system or browser up-to-date.
https://www.ebay.com/help/policies/resolving-technical-issues/technical-issues?id=4220
Non-recommended browsers may work but are not guaranteed to do so. But even recommended browsers are not guaranteed to work all the time, for every feature.
When using an older version of a browser or a non-standard browser, many things may work fine, but certain features may fail.
There are many reasons why an eBay feature may not work -- some due to things on eBay's end, some due to network conditions, and some due to things on the user's end. A difference in a browser's cache, cookies, settings, version or add-ons may affect how things work. Conflicts with security or privacy software or settings can also cause issues.
Sometimes a problem is caused by a change on eBay's end, but that problem may still be worked around by a change at the user's end -- such as by clearing a browser cache or deleting eBay cookies. Changes by eBay don't always cause problems for every user, but users with certain unique history may experience problems. The problems may go away eventually as cache data is overwritten or cookies are updated in the normal course of events, but that process can be speeded up by the user.
Trying another browser is a quick way to see if a problem is isolated to one particular browser.
If a feature fails in one browser but works when tested in another browser, that simultaneously allows the user to work around the immediate feature issue, and also provides some indication of things that might be worth trying: such as updating the problematic browser, clearing cache or deleting eBay cookies, changing settings, or temporarily disabling add-ons to discover if one is causing a conflict.
