You are receiving the "protocol violation" error because the header in the negotiation request is considered "unsafe," resulting in the rejection. Please check the certificates on the WFA host and the NetApp Cluster were installed correctly. In addition, you must stop the WFA Database and WFA Server services prior to replacing the certificates and restarting the services afterward.
Here is a reference document walking you through how to update the WFA certificates:
Accessing the log through the web interface, in wfa.log show recurring Java error :
2020-11-26 05:56:45,751 WARN [com.netapp.wfa.common.io.ExecutionUtils] (Thread-157 (ActiveMQ-client-global-threads)) Exception while getting password from Vault:: org.jboss.security.vault.SecurityVaultException: java.lang.IllegalArgumentException: Null input buffer
I won't paste the full stack but some interesting lines (IMO) :
Caused by: java.lang.IllegalArgumentException: Null input buffer