This article introduces the method that resolved the issue of folders not mounting in VirtualBox Windows 10.
Normally it should mount like this, but sometimes it doesn’t display.
virulbox winodws mount not work - Google Search
[virtualbox - Can't access shared folder with Virtual Box - Super User](https://superuser.com/questions/1116724/cant-access-shared-folder-with-virtual-box)Install the VirtualBox Guest Additions Plug in.
From Console File → Device → Insert Guess Additions Image CD.
I tried reinstalling Guest Additions as a last resort and it worked.
The key point is that it’s a reinstallation.
If VBox had even a single message like “there’s a new version of Guest Additions available, please install it,” this would have been resolved immediately, but since there’s nothing like that at all, it was quite troublesome.