Hi! I understand you're having trouble opening your inbox in the eclipso Mail Europe app on your Mac with OS X 10.15. Let's work together to get this fixed.

To help me understand better, could you tell me if the app opens at all and whether you see any error messages when trying to access your inbox? Also, have you recently updated the app or your operating system?

Meanwhile, here are some basic steps that often resolve inbox access issues in the eclipso Mail Europe app:

1. Restart the app: Sometimes closing the app completely and reopening it can resolve temporary glitches.

2. Check your internet connection: Ensure your Mac is connected to the internet and the connection is stable.

3. Update the app: Check the Mac App Store for any updates to the eclipso Mail Europe app. Running the latest version helps prevent bugs.

4. Re-login: Log out of your eclipso account within the app and then log back in. This refreshes your session.

5. Check email access settings: If you use IMAP/POP settings, verify they haven’t changed by going to eclipso webmail settings and ensuring that access for email clients is enabled.

If these steps don't resolve the issue, we can try some more advanced troubleshooting like checking permissions on your Mac, clearing app cache, or reinstalling the app.

Let me know what you observe when trying these steps or if you want me to guide you through any of them in detail!