Today I updated my Varia Radar to version 3.00 and the Edge 520 to version 3.10. This doesn't solve my problem. I could not use the radar sensor. The varia is connected to the edge. The connect symbol top right is shown, but no vehicle column. color overlay: on, vehicle colum: right, tones: on. The varia status led shows green during switch on and switches to off after start. So there should be no varia failure.
In demo mode the vehicle column is shown as expected. What now? Sending the device back? The garmin support says update should solve the problem, but they didn't say which versions may solve the problem.