I made an attempt to mount again through Dolphin (as previously explained). The message this time is: "An error occurred while accessing 'Storage', the system responded: The requested operation has failed: Error mounting /dev/sdb3 at /run/media/george/Storage: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=100,dmask=0077,fmask=0177" "/dev/sdb3" "/run/media/george/Storage"' exited with non-zero exit status 21: fuse: mount failed: Device or resource busy "