There are occasionally in a cluster environment that users accidentally delete their head node SSH keys and later cannot submit their jobs to the queue or their MPI jobs cannot scale beyond 1 node. The system you will see when you turn on the verbose method

To conduct a quick test,

# ssh -v remote-host

you will see an errors similar to  such as those below:

debug1: Unspecified GSS failure.  Minor code may provide more information
Unknown code krb5 195

OR

debug1: Miscellaneous failure
No credentials cache found

To reinstate the password-less access to compute nodes, you have to do the following. First thing first, please do backup files at your ~/.ssh/

Step 1: Regenerate the SSH keys
SSH Login without Password

Step 2: Append the public keys ~/.ssh/id_rsa.pub and put into the ~/.ssh/authorized_keys

# cd ~/.ssh/

# cat id_rsa.pub >> authorized_keys

# chmod 400 /home/myuser/.ssh/authorized_keys

Step 3: Try ssh into the compute nodes. It should be clear password-less access to all nodes.