In this post No App display in App Lounge - #4 by aibd I expand on my experience of “token exchange” being the problem.
However if apps Search and display works and apps are installing ok but a list of apps is not updating is something else.
One thought is App Lounge attempting to update an app which originally came from a different source? App Lounge > Settings includes a check box to prevent this.
Settings > Apps > your_app will show under STORE the original source of the app.