This is very interesting; I have an 800v4DAX where I am unable to establish contact with the DV20 board. I am therefore very keen to learn how to bring the DV20 board back to life. I’m wondering, though, if this affects all the boards or if only one of them has been "bricked."
For reference, the boards in question are the DV02, DV12, and DV20.

TV room: 861v8, 800v4, UHD722,Front 2xDSP7200SE, DSP7200HCSE, Side DSP5200, Rear DSP33, DSW, (DD 15 Sub),
Roon Rock NUC, QNAP NAS, Chromecast Ultra, Apple TV, Oppo BDP-105D, Pro-ject Pre box S2 digital, Philips Pronto remotes, Supra LoRad Power.
Office: 800v3, MS200, DSP3100
Basement: MS600, 502, 557, Dynaudio 52se, Dynaudio Sub 250