For now we have to select an object as material receiver before open the LiveDB windows. Otherwise blender will show an warning info - "Please select an object as LiveDB material receiver".
Is it the reason of this issue? If so, it will be fixed in the next build - we are going to provide a more flexible livedb material assignment way in the next major v4 build. Currently, 16.3.2 is on the way with fixes for most of the reported critical issues, so new feature might be included in 16.3.3.