zScaler NSS Connectivity to MCAS

We have configured a zScaler NSS server but we are not receiving any logs to MCAS.

We can telnet to the portal URL and blob storage addresses on 443, but a curl command with the correct token fails to connect with "error:1407742E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert protocol version"

Is there network configuration that we are missing, or anyway to further diagnose this problem.

Thanks