An agent is defined to WAAE that is defined with the 'encryption_type' attribute set to 'AES' and a custom key is specified in the 'key_to_agent' attribute. If the 'encryption_type' attribute is set to 'DEFAULT', the autoping will succeed.
This error occurs when the cryptkey.txt file stored on the agent machine is not valid for the custom encryption key specified in the agent's machine definition in WAAE. This can be further verified by checking the 'receiver.log' file on the agent machine under '<AGENT_INSTALL>/log'. You will see an error containing the following text when the message arrives from the WAAE Scheduler/App Server machine...
cybermation.library.communications.CybConversationException: Bad padding
If you have another agent that is working fine and is using the same custom encryption key, you can simply copy the cryptkey.txt file in binary mode from the working agent to the failing agent and then restart the agent service on the failing agent machine.
If you do not have another agent that is working using the same custom encryption key, you will need to create a cryptkey.txt file for the custom key and place it on the failing agent machine. The cryptkey.txt file can be generated using the as_config utility located on the WAAE server. For details about the as_config utility, please consult the online documentation for WAAE.