Quobuz unavailable album tracks

Why are some tracks on Quobuz albums “unavailable”? the latest example of this is the title track on Grazing in the Grass: The Best of Hugh Masekela

Hi Philip,

In this example, it looks like it must be the record label for this artist doesn’t allow streaming of this track on this album, for some reason.

I checked both Qobuz and Tidal apps, and they both have the first track as unavailable.

Cheers, Greg