I figured it out. Somewhere along the way it was advised to run jackd (server) as administrator. The issue was that the Dorico running as a normal user couldn’t open the named pipe and hence, JackRouter driver returned failure. As soon as I started Dorico as administrator, everything works. I have the main jack server running on my mac set up as networking master. I have the other jack running on my windows machine setup as net slave … pretty cool.
Why Dorico doesn’t report the driver initialization failure is another thing, I guess.