Do you have a load balancer/proxy in front of Tableau Server? Typically in this situation, you'd place a load balancer in front of Tableau Server - and use the load balancer url when configuring Tableau Server for Kerberos. Using this approach, the same keytab and configuration files could be used for the active and backup primary computers.
Note: Verify the host names in the setspn lines of the script. If you are using an external load balancer or a reverse proxy, the host names should match the name you used when you configured Tableau Server for the load balancer or proxy. If you have not configured Tableau Server for your proxy or external load balancer, do that and then re-export the Kerberos configuration script to ensure it has the correct host names. See Add a Load Balancer and Configuring Proxies for Tableau Server.