What version of Android?
Make sure you have the latest version for your operating system.
https://community.ebay.com/t5/Android-App/Android-app-not-supported-on-older-systems/m-p/30652449/hi...
Try uninstalling the eBay app, restarting your device, then installing the latest version of the eBay app from the Google Play Store. The restart in between should ensure a clean install.
