For some reason, using something like

mount -t cifs //10.1.1.1/share /mnt/share -o credentials=/etc/credentials.conf 

will fail with permission denied, when

smbclient //10.1.1.1/share -U DOMAIN\\Administrator

works just fine.

This seems to be an issue with how the command line is parsed.

If you add something like

//10.1.1.1/share /mnt/share cifs vers=3.0,credentials=/etc/credentials.conf 0 0

into /etc/fstab

then reload the daemon with

systemctl daemon-reload

then mount with

mount -a

you will find this mounted just fine! Fantastic