Unable to give 'plex' user permission to external NTFS hard drive

I have an external drive that works fine when using it as myself.

When the 'plex' user tries to access it is does not have permissions.

I've added the following to /etc/fstab:

UUID=40CAE69ACAE68B8A /media/james/Twenty1 ntfs-3g defaults,uid=999,gid=999,umask=0002 0 0

Then I umount and mount

sudo umount /media/james/Twenty1sudo mount -asudo chown -R 999:999 /media/james/Twenty1

But when I check the permissions they don't look right:

mount | grep Twenty1/dev/sdb1 on /media/james/Twenty1 type fuseblk (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096)

And:

sudo -u plex ls /media/james/Twenty1ls: cannot access '/media/james/Twenty1': Permission denied

Am I doing something wrong?