Hi there! I see that your Lingo app is showing only a white screen on your Mac with OS X 10.15.7. Let’s get that sorted out.

To clarify before we proceed:
- Is this happening only when you open the app, or does it happen after you try to log in or perform a certain action?
- Have you recently updated the app or your macOS?
- Did this just start happening, or has it been an ongoing issue?

Meanwhile, here’s a step-by-step set of general troubleshooting steps that often help resolve a white screen issue in applications like Lingo:

1. Force Quit and Restart the App
- Click on the Apple menu (top-left corner), select “Force Quit…,” find the Lingo app in the list, and select “Force Quit.”
- Then, reopen the Lingo app fresh.

2. Check for App Updates
- Open the Mac App Store, go to “Updates” and ensure the Lingo app is up to date. If there’s an update, install it and try again.

3. Restart Your Mac
- Sometimes a simple reboot can clear any temporary glitches.

4. Clear App Cache / Preferences
- Since macOS apps often store preferences in the Library folder, try this:
- In Finder, press Command + Shift + G
- Enter ~/Library/Preferences/ and look for any files with “Lingo” in the name (e.g., com.lingo.app.plist), and move them to Trash temporarily.
- Restart Lingo and see if this helps.
- Note: This resets some app preferences but won't delete your account data.

5. Check Your Internet Connection
- The Lingo app may need an active connection to load data. Confirm you have a stable internet connection.

6. Uninstall and Reinstall the App
- Drag the Lingo app from the Applications folder to Trash.
- Download and install the latest version from the Mac App Store again.

If these steps don’t resolve the white screen, there might be a deeper issue such as an incompatibility or a bug introduced in a recent update. Let me know what you have tried, and we can dig further or explore account-related checks next!

Are you able to try this and tell me how it goes?