So, Ebay redesigned their apps and basically made a complete mess of it.
I’m not going to rant, just tell you how to get the old app back.
First, find somewhere safe to download it from: Amazon.
Second, in the internet browser on your phone or tablet go to Amazon Underground and install the Underground App.
Third, start the Amazon Underground app (it looks similar to the Google Play one) and navigate from the menu to “Apps & Games”.
Fourth, search for Ebay, “buy” it (it’s free).
Fifth, back to the menu, then “Your Apps” under Library. Then click “Cloud”. There you will see Ebay with an install button next to it. Sure you can figure out the rest!