Trying to establish an SFTP connection with key exchange and get this error
com.sshtools.j2ssh.transport.publickey.InvalidSshKeyException: The key format is not a supported format
The Key used in the Key Manager activity is not OpenSSH compatible
A) Convert the key to OpenSSH
Use OpenSSH tools to convert the key to OpenSSH format. You should then be able to use the converted key with j2ssh.
B) Generate a new key pair using j2ssh or OpenSSH tools
You can also generate a new key pair using OpenSSH tools (ssh-keygen) and then upload the public key to the server