I think the latest update of the app is very glitchy in general. I don't have this exact problem, but what happens to me is that when I tap a push notification to read a new message it pops up, but it's blank. The only way I can read the message through the app is to manually stop all my apps and re-open the ebay app. Another weird feature of this latest update I've noticed is that when I tap notifications to see items that are ending soon it does not send me to that item. It usually ends up sending me to the previously ending item before it on my watch list. Very buggy.
Wow, I didn't know there were so many issues with the new version of the app! I always have other apps open, so I will try closing them and reopening the eBay app to see if they does he trick.