@rob-l - if the fileserver where your movies directory is sharing with SMB3.0 for Windows 10, and you need credentials to access the files, you need to change the security options from ntlm to ntlmssp.
Then to grant permissions to read write, you need to specify user group gid or user uid. Easiest to specify a user than a group, otherwise you'll need to convert the Windows Security Group to a Unix gid.
//192.168.0.200/Movies /mnt/NAS1HD cifs username=XXX,password=XXX,iocharset=utf8,sec=ntlm 0 0 ```
Then, if you want it to mount when it receives connectivity, use _netdev as the final option
//192.168.0.200/Movies /mnt/NAS1HD cifs uid=ubuntuusername,username=XXX,password=XXX,iocharset=utf8,sec=ntlmssp,_netdev 0 0
You can also store the credentials in a file with permissions:
echo username=NETWORKUSERNAME > ~/.smbcredentials
echo password=NETWORKPASSWORD >> ~/.smbcredentials
CHMOD 600 ~/.smbcredentials
//192.168.0.200/Movies /mnt/NAS1HD cifs uid=ubuntuusername,credentials=/home/ubuntuusername/.smbcredentials,iocharset=utf8,sec=ntlmssp,_netdev 0 0
... and just reading through the rest of the stuff here, what organic-marble has vers=3.0 is an alternate choice to sec=ntlmssp