Cannot change Default Volume Profile when HDRP is not active

Fresh install of Unity 6, new empty HDRP project.

I create my own HDRP Asset, Default Volumes, and Quality Settings by duplicating existing, out of the box assets.

In Project Settings > Graphics, I drag my new HDRP Asset into the “Default Render Pipeline” field. No problems there.

When I try to drag my new Default Volume profile into “Volume > Default > Default Profile”, I get this console error:

Cannot change Default Volume Profile when HDRP is not active. Rolling back to previous value.

I don’t understand the meaning of the error. HDRP is indeed “active”!

Any idea why I cannot change the Default Volume Profile in this way? Has something changed in Unity 6 HDRP config that I’m missing?

Many thanks!