Sorry for replying in English but I suspect that your calibre library folder was originally installed in your Documents directory. With the Windows 10 upgrade, you have run into Controlled Folder access. See
Personalizzare l'accesso controllato alle cartelle for more information on that.
You can either turn allow calibre to access your current library (see the Utilizzare l'app Windows Defender Security per autorizzare app specifiche section in the web page linked above) or you can move your calibre library into the root of your User directory.
To move your library, exit from calibre. Create a new directory in the root of your user folder ( I used calibre as the name). Copy your library from the Documents folder into the new calibre folder. Open calibre, use the dropdown menu on the Library icon, click on Switch/Create Library, select Use the previously existing library at the new location, browse to your new library location and click OK.
Once you are happy that your new library location works, you use the dropdown menu on the Library folder to select Remove Library to remove your old library.