I have the Sales app plus two custom apps in a production instance. I have created a sandbox instance and done a full copy from production to sandbox. https://home.dynamics.com however is only showing tiles for the apps in production, there is nothing there for sandbox. The same is true of the Dynamics 365 drop down that shows available apps, nothing for sandbox.
I know the sandbox apps are present because I can navigate to them by modifying the URL for the production app to point at the sandbox instance. I have tried clearing cache, syncing on the home menu and logging off/on.
I have an outstanding request open with Microsoft, but they don't seem to know much about this.