Generating a Certificate Signing Request (CSR) Using Zymkey

Hi,
I have successfully used Zymkey as the client side of mutual TLS authentication when the CSR is created with the zk slot 0. However, if I try the same using e.g. zk slot 1, it fails. The CSR file is created, and a certificate is created by signing with my CA cert, but the TLS authentication fails.

I have set the env var ZK_SSL_SLOT=1 for the CSR command as described here: Creating CSR - #2 by Bob_of_Zymbit

How can I use zk slot 1 or 2 for the CSR?