Hi! I see you're having trouble with the Y-Disk app on your Mac running macOS 10.15.7—it opens but then closes immediately, is that right? Let's work together to get this sorted out.

To start, can you tell me if this happens right after launching the app every time? Also, have you tried any fixes like restarting your Mac or reinstalling the app already? That will help me avoid repeating anything you've done.

In the meantime, here are some initial troubleshooting steps that often help with app crashes on macOS:

1. Restart Your Mac: Sometimes a simple reboot clears any temporary glitches affecting apps.

2. Check for App Updates: Open the App Store, go to the Updates tab, and see if there's a newer version of Y-Disk available for your macOS version. Running the latest compatible version is important for stability.

3. Reinstall Y-Disk: Since you probably know this, but it’s good to be explicit — delete the app completely by dragging it to the Trash, empty it, and then reinstall it fresh from the official source.

4. Check macOS Updates: Even though you’re on OS X 10.15.7 (Catalina), verify in System Preferences » Software Update that you have all the latest patches. Sometimes OS updates fix compatibility issues.

5. Look at Console Logs: If you’re comfortable, open the Console app (in Utilities), then launch Y-Disk and watch for any error messages or crash logs appearing at that moment. These logs can provide clues.

Once I know more about your attempts so far, I can suggest deeper steps if needed, like deleting the app’s preference files or checking for conflicting software.

Let me know what you find! Are you comfortable trying these?