Mounting 2nd internal HDD

i have an internal 4TB NTFS hard disk all my music stored in using volumio PC version , i tried to mount it by using different guides, but non is working.
I managed to get the HD auto mounted using this guide https://forum.volumio.org/volumio-mini86-support-thread-t7875.html. but couldn’t get volumio scan it to add my music to library, it seems all scanning process gets corrupted once i edit rc.local.
Then i tried https://forum.volumio.org/use-second-for-storing-music-t6939.html the changes i made in ‘/etc/fstab’ never get saved after rebooting.
Then i decided just to mount it and then add it manually in NAS section . created auto mount using startup script https://forum.volumio.org/service-startup-t7524.html. the drive gets mounted the unmounted as shown below.

volumio@volumio:~$ systemctl status MYHD.service ● MYHD.service - MYHD
Loaded: loaded (/etc/systemd/system/MYHD.service; enabled)
Active: inactive (dead) since Tue 2020-03-24 05:46:47 UTC; 1min 12s ago
Process: 583 ExecStart=/usr/local/sbin/MYHD.sh (code=exited, status=0/SUCCESS)
Main PID: 583 (code=exited, status=0/SUCCESS)
Mar 24 05:46:45 volumio systemd[1]: Started MYHD.
Mar 24 05:46:46 volumio sudo[584]: root : TTY=unknown ; PWD=/ ; USER=root ;…00
Mar 24 05:46:46 volumio sudo[584]: pam_unix(sudo:session): session opened f…0)
Mar 24 05:46:47 volumio sudo[584]: pam_unix(sudo:session): session closed f…ot
Mar 24 05:46:47 volumio ntfs-3g[778]: Version 2014.2.15AR.2 integrated FUSE 28
Mar 24 05:46:47 volumio ntfs-3g[778]: Mounted /dev/sda2 (Read-Write, label …1)
Mar 24 05:46:47 volumio ntfs-3g[778]: Cmdline options: rw,noatime,dmask=000…00
Mar 24 05:46:47 volumio ntfs-3g[778]: Mount options: rw,allow_other,nonempt…96
Mar 24 05:46:47 volumio ntfs-3g[778]: Global ownership and permissions enfo… 7
Mar 24 05:46:47 volumio ntfs-3g[778]: Unmounting /dev/sda2 (Mro)
Hint: Some lines were ellipsized, use -l to show in full.
volumio@volumio:~$ df -hT
Filesystem Type Size Used Avail Use% Mounted on
overlay overlay 115G 79M 109G 1% /
/dev/sdb2 ext4 2.7G 1.2G 1.4G 47% /imgpart
/dev/loop0 squashfs 579M 579M 0 100% /static
devtmpfs devtmpfs 1.4G 0 1.4G 0% /dev
tmpfs tmpfs 1.4G 83M 1.3G 6% /dev/shm
tmpfs tmpfs 1.4G 5.0M 1.4G 1% /run
tmpfs tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs tmpfs 1.4G 0 1.4G 0% /sys/fs/cgroup
tmpfs tmpfs 1.4G 28K 1.4G 1% /tmp
tmpfs tmpfs 1.4G 0 1.4G 0% /var/spool/cups
tmpfs tmpfs 20M 60K 20M 1% /var/log
tmpfs tmpfs 1.4G 0 1.4G 0% /var/spool/cups/tmp
/dev/sdb1 vfat 487M 32M 455M 7% /boot
tmpfs tmpfs 279M 0 279M 0% /run/user/1000

can you please assist me in this issue , FYI i am below average user in Linux.