I’m on Ubuntu MATE 18.04, so assuming that the Samba packages haven’t changed too much between both versions, don’t you have smbd and nmbd in /etc/init.d?
If you check the processes list with ps -A | grep smb there’s no smbd running?
Also, have you installed only the samba package? You might need other packages that are not automatically installed, like smbclient. And if you want to share folders through Caja, you’ll need to install caja-share (though it might offer to install it automatically the first time you try to share a folder).