Since the share will mount when you issue a
sudo mount -a I suspect there is nothing wrong with your fstab declaration. It does suggest a timing issue. Linux is reading fstab before the network stack is up and operational so when it goes to mount the network share it fails.
2 possibilities are to turn this into a "mount on demand":
 Keep your current mount point but add two more options:
//192.168.100.12/HomSpace /media/nasMounted cifs credentials=/root/.memoriaCredentials,uid=1000,gid=1000,noperm,rw,vers=3.0,noauto,user 0 0
When you boot your system the share will not mount but it will show up on the side panel of your file manager as a launcher. Click on it and it will go to fstab to see how to mount it then do so.
EDIT: As pointed out below I should have made sure the credentials file was readable by the ordinary user for this method to work. Placing it under one's home directory would be a better choice.
 Change your mount point and use a systemd automounter.
Mount point cannot be under your home directory or /media so I would suggest something like /mnt/nasMounted. Then add two options
//192.168.100.12/HomSpace /mnt/nasMounted cifs credentials=/root/.memoriaCredentials,uid=1000,gid=1000,noperm,rw,vers=3.0,noauto,x-systemd.automount 0 0
This works by accessing the /mnt/nasMounted mount point. Either by you directly through the file manager, or by any application, or by any other process. Pretty much anything accessing that mount point will trigger a mount all without your intervention.
Either way after you edit fstab run these two commands to make systemd happy:
sudo systemctl daemon-reload
sudo systemctl restart remote-fs.target