Offline access to the Knowledge app needs to be refreshed every 10 days. In this way you can ensure you have the most up-to-date content.
If you currently have access to AMBOSS, but have trouble accessing the Knowledge app, you can refresh your offline access as follows:
Tap on the app Settings > tap Offline Access > Refresh
To update the content of your app, follow this path:
Tap on the app Settings > tap Library > Check for update