Now this answer is for those lost souls that got here with this problem because they force-unmounted the drive but their hard drive is NTFS Formatted. Assuming you have ntfs-3g installed (sudo apt-get install ntfs-3g).
sudo ntfs-3g /dev/hdd /mnt/mount_point -o force
Where hdd is the hard drive in question and the "/mnt/mount_point" directory exists.
NOTES: This fixed the issue on an Ubuntu 18.04 machine using NTFS drives that had their journal files reset through sudo ntfsfix /dev/hdd and unmounted by force using sudo umount -l /mnt/mount_point
Leaving my answer here in case this fix can aid anyone!