When performing a search in the AppStore and navigating the “Results for… collection” using VoiceOver, it is not possible to activate links with VO-Space. You should be able to press VO-Space to activate a link, or interact with the link to access the “Get” button if you wish to immediately download the app.
Bug First Encountered
How often the bug occurs
Route the mouse pointer to the link by focusing on it and pressing VO-Command-F5 (or VO-Command-Function5 if you're using a Mac with a Touch Bar) and click the mouse button.