Do you have MConfig? You might have to do a bit of configuration of your HD621, (and possibly your master speaker) by the sounds of it…

Firstly, though, try this:

Put the system into standby. Press the CLEAR button on the MSR remote. You should see the master speaker flash up that it is controller. You won’t see anything on the HD621, as it’s got no alphanumeric display, but this will at least tell it that it is not the controller in the system.

Then bring the system out of standby by selecting a known source.

Post back with what happens when you have done this.

HC: 861v4/ID40/LPS, DSP5000, DSP5000VC, DSP3100, SW1600, HD621, Oppo BDP-105, Sony VPL-HW55ES
2-Channel: Oppo BDP-105, TEAC VRDS-7/Trichord Clock 3/PSU, 551, Quad 303, Harbeth Compact 7ES-3, Kimber cables, Russ Andrews mains and supports.
Previous Meridian: 5000C, 5200SL, 7200.2, 6000, 562V.2, 568.2mm, 800v4, 808.2i, 818v2/v3, 861v8, 502