matched no descriptors

I encountered an issue when running the last part of the step-by-step tutorial, using a different PDB file, 

./run.sh PDB_exampleA

Starting to match target descriptor to descriptors from 3 proteins; this may take a while.
matched no descriptors

While the 4QVF example completed successfully, another sample PDB did not. I am not sure the meaning of "matched no descriptors" 
