Fully uninstall and reinstall G HUB:

1. Open “Force Quit” from the Apple menu.
2. If present select Logitech G HUB and choose “Force Quit”
3. Quit G HUB from the Apple Menu
4. Open Finder
5. Select “Applications”
6. Right-click on Logitech G HUB and select "Move to Trash" or drag to the Trash can in the dock.
7. Please then restart your system.
8. Reinstall G HUB via the following link https://www.logitechg.com/en-gb/innovation/g-hub.html
9. System Extension Blocked dialog for "lghub_system_tray" should appear.  Open System Settings and allow "Logitech G HUB" in Privacy & Security settings.  A second System Extension Blocked dialog should appear.  Please do the same and allow "Logitech G HUB"

If issues persist, run G HUB with the default settings:

1. Exit G HUB by right-clicking the G HUB icon in the menu bar and selecting Quit.
2. Click on Go > Go to Folder.  Enter the path ~/Library/Application Support/LGHUB
3. Find settings.db and make a copy and back this up somewhere on your computer. The Desktop is a good place so you can find it easily.
4. Delete the settings.db file in the LGHUB folder.
5. Launch G HUB. You will notice that all the settings have been set back to default and the settings.db file has been rebuilt.

Restoring the software's old settings:

1. Quit G HUB.
2. Copy and paste the backup of settings.db that you saved earlier into  ~/Library/Application Support/LGHUB
3. Launch G HUB — your old settings should be restored.