For a few days ago Microsoft release a new big update for Windows 10. After the update my share of my host machine didn´t work to my Windows 10 VM. I looked around a lot on internet. But to conclude the simple solution was just to reinstall the Guestaddition in windows and reboot and all worked as it should again. Adding this post and hope it will help someone else.
Tags: shared folder, VirtualBox, Windows 10