MTRX Studio doesn't show up in Dante

[Cheesehead]

I used to have 2 outputs from my MTRX Studio going to Dante, which showed up in Dante Via. I was then able to route these outputs through Dante via to use them as a stereo send for remote mixing in Sessionlink Pro.

I had this working on a Mac trashcan running Mojave, but I'm now on a 2019 Mac Pro on Catalina and using exactly the same network setup, cabling and switch, it doesn't work.
The MTRX Studio no longer shows up in Dante Via?

I have port 1 on the MTRX Studio connected to a switch which then goes into one of the ethernet ports on the Mac. Dadman is working fine and sees the MTRX Studio, but nothing shows in Dante. Either Via or DVS?

Any advice gratefully received.