Some app issues can be helped by uninstalling the eBay app, restarting your device, then installing the latest version of the eBay app. The restart in between should ensure a clean install. If the problem had to do with the previous installation, that may help.
If not, you may want to post on one of the App boards; there are eBay folks that read and respond to app issues there that may be able to provide more help. Be sure to include your device model along with the operating system version, and the version number of the eBay app.
https://community.ebay.com/t5/Android-App/bd-p/androidapp
