Have you tried the obvious - switch the unit off then on again and then connect to it via the PC before you press any buttons on it?

Some units won't go into configuration mode unless they are reset...

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5k.2C, DSP33, F80
Spare: MCD, 100 Series, 200 Series, 500 Series, C15s.