I do not have an iOS device to test, but the Android version of the app seems to be working for me, and providing search results.
Some things to check if you have not already done so:
Make sure you have the latest version of the app. For Android that is 6.161.0.1 -- for iOS the number is likely similar, though may have only three segments instead of four. Older app versions may be erratic.
Make sure you do not have any locked filter settings that might be preventing you from seeing results. If you see a number over the Filter menu, that indicates active filters.
Make sure you have not inadvertently changed your location setting to somewhere inaccessible that no one ships to.
Try manually deleting the eBay app, restarting your device, then installing the latest version once again. If the problem was with a previous installation not finishing cleanly, the restart in between should ensure a clean install this time.
