If it is not work it is mean you have not oldschool foretrex 401 with ID 006-B1021-00 and 006-B1020-00. I did not read your first post with big passion because for oldschool foretrex it was the first step for repair to do "non-volume reset" with batteries trick. Now I have read the post and my ruined brain say me what no masstorage and so garmindevice.xml in this devices.
What ID do you have for your unprecedented animal?