We try to enable sftp for a couple of accounts without good results. Any help are welcome.
we are working on sles 12
Hi and welcome to the Forum 
If ssh is enabled and the ssh ports is open in the firewall it should just work out of the box, no admin input required?
Can you ssh onto the box? Maybe ad some debug -vvv to see what is happening.
What clients are you using to connect to the server?
Are multiple users connecting to one area on the server, then it may be group ownership and/or permissions.