Provisioner SSH Access Failed (Connection Timeout)

[Qmatteo]

During the provisioning process it seems that the "null resource" is not able to connect to the EC2 instance.

This is the error that I get:
"Error: timeout - last error: SSH authentication failed (dc01@18...**:22): ssh: handshake failed: ssh: unable to authenticate, attempted methods [none], no supported methods remain"

Any ideas?