Not that it should matter, but did you try setting it with your C15? I haven't used volume leveling in awhile but it worked fine when I did. It was surely several firmware updates ago.

Regards,
Bill

Theater: 861v8+ID41, 218, (2) DSP8KSEs, DSP7200VCSE, (2) DSP5200s, Marantz UD9004, (2) JL Audio F113s, Roon
Whole House: 218s, DSP520s, DSP 320s, Roon
Office: 218, DSP3200s, Roon