I raised a ticket with IBM. They advised that in IBM/WebSphere/AppServer/java/8.0/jre/lib/security/java.security there is a "# List of providers and their preference" orders. In that list, it is important that IBMJCE be listed above IBMJCEPlus.
This is the order I found:
security.provider.1=com.ibm.jsse2.IBMJSSEProvider2
security.provider.2=com.ibm.crypto.plus.provider.IBMJCEPlus
security.provider.3=com.ibm.crypto.provider.IBMJCE
Based on IBM's comments, I switched IBMJCE and IBMJCEPlus. The above lines now look like this:
security.provider.1=com.ibm.jsse2.IBMJSSEProvider2
security.provider.2=com.ibm.crypto.provider.IBMJCE
security.provider.3=com.ibm.crypto.plus.provider.IBMJCEPlus
I then tried to start the software, and it started without issue.
#Support#SupportMigration#WebSphereApplicationServer(WAS)