Using the Camino browser on eBay solved my listing problems. Now eBay works and PayPal works! One of my earlier browsers had failed on PayPal by not displaying the Withdraw tab which, you can appreciate, was a pretty important drawback on a banking site. Using Camino, I can see and press that missing tab.
Now, I occasionally look at the eBay HTML and Tech chat boards to see what problems Mac users are reporting. They are often reporting glitches I recognise but which I no longer experience. I can only assume that they don't have Camino.

Camino comes from Mozilla, the home of Firefox. Camino is a free download at

At the time of writing Camino is an Apple software download "Staff Pick" on Apple's website.

An outdated browser is only one source of problems so make sure that all the hardware and software elements of your online setup are up-to-date.

Disclaimer: it is for you to determine whether Camino is appropriate and "safe" for you to use. I draw attention to it for informational purposes only.