Some sources (especially Google Drive) allow characters in file and folder names that are considered "illegal" on some operating systems. When this happens, odrive can't create the file or folder on the local system, so it is not shown.
Typically this is seen with the following characters:
' ' (leading or trailing whitespace)
This can also happen in the files/folders have characters or patterns that fall into our "ignore" list: https://docs.odrive.com/docs/sync-changes#section--ignore-list-
If you remove those characters the files/folders will show in the odrive desktop client.