Under system preferences, security & privacy, firewall - try disabling your firewall temporarily as a test. Is this the first time you’ve installed Roon or was it working before on another device in your house?
I’m not sure if your Mac-mini is connected via wifi or ethernet cable, and I assume by ‘green lock light’ you mean the ‘connected’ light on the Apple-system-preferences-network panel. Two things you can check - 1) if you remember the IP address of your previous Roon-core device, make sure it is the same as your new Mac-mini. or 2) login to your Mac-mini, open a terminal screen, and ping the IP address of your DS (which you can get from the DS’s display screen.). The ping should go directly from the Mac-mini to the DS and not go through a router/default-gateway.
It’s connected via Ethernet. By lock light, I meant that, in the DS on the Bridge screen display, the network symbol is green.
No, in hindsight I should have noted the address. I assumed that that, too, would copy over, and there is a number in the network preferences, but I can’t say for sure that it’s the same.
When the sun comes up (I’m in LA), I’ll do the 2nd thing suggested.
Your MAC is 192.168.1.4 and received this IP via DHCP. The default-gw for your network is 192.168.1.1. This is all good. The weird thing is you said your DS has an IP of 192.168.1.1 - this is the same IP that your MAC thinks should be the default-gw. The DS should have an IP of something like 192.168.1.5 with a default-gw of 192.168.1.1.
If you turn your DAC off with the switch on the back, wait for a couple of minutes, and turn it back on, it should ask (automatically) for a new IP address. After it restarts, wait a few minutes and check the IP address. If it is unchanged and/or Roon can’t find it, post a picture of your DS screen that shows the IP addresses here.