Hi there! I understand you're having trouble accessing the Face Gallery in the H Band app on your Mac with OS X 10.15. Let's figure this out together.

To start, could you let me know if the app is opening normally and if other features are working fine? Also, have you tried any steps already, like restarting the app or your device?

Meanwhile, here’s a step-by-step to try that often resolves gallery access issues:

1. Fully close the H Band app on your Mac. You can do this by right-clicking the app icon in the dock and selecting Quit.
2. Restart your Mac to clear any temporary glitches.
3. Open the H Band app again and try accessing the Face Gallery.
4. Ensure your internet connection is stable since the Face Gallery may need to fetch watch faces from the cloud.
5. Check if there’s an update available for the H Band app in the Mac App Store or the app’s official website. Sometimes bugs affecting certain features are fixed in updates.
6. If after that the gallery is still inaccessible, try logging out of your account inside the app and logging back in, as this can refresh permissions and data.

If that doesn’t do it, the issue might be related to the app’s cache or a need to reinstall it. You can try uninstalling the H Band app completely and then downloading and installing the latest version again.

Let me know how these steps go or if you notice any error messages or anything unusual when you try to open the Face Gallery. We can then dig deeper based on that!