SFTP uses the ssh server so if tou have a root console open and type "ps x" then it should be in the list if it is loaded. If it isn't loaded then find it with
find / -name sshd
then change to the directory it is in and type
./sshd
That will run the SSH daemon
Once running go to a PC on the network, open a root console and type
ssh "IP address"
If that works then you will be able to open an sftp session using nautilus or any sftp software.