I got it working! The critical piece of information was this.
“The certificate in the list must be one of the issuer certificates used to sign the client certificate being used if not then the client will not provide any certificate for validation. Additional note that unless the certificate is self-signed you can not provide the client public certificate as part of this list.”
I was indeed including my specific personal cert, that is signed by the 3M CA. I needed the 3M CA intermediate that signed it on the gateway.
Thanks Steve, I don’t think we need our scheduled WebX now.