[root@ns58744 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md1 10G 10G 0 100% /
/dev/md2 683G 7.4G 641G 2% /home
/dev/shm 2.0G 0 2.0G 0% /dev/shm
Your filesystem on / is full.
If you login via SSH or SFTP software, you should be able to access your files and remove something off /
You have used your 10GB of space mounted to / (but still have 641 GB of space left for files in /home). Because of this, the user files cannot be read/written to correctly and so the login cannot be authenticated.