cannot run "CGA_WES_Characterization_Pipeline_v0.1_Dec2018" pipeline for paired tumor analysis

I try to run the "CGA_WES_Characterization_Pipeline_v0.1_Dec2018" pipeline for paired tumor analysis on Firecloud.
A common error that I get is “expected single value for workflow input, but evaluated result set was empty”. I modify the workflow inputs, but I get error again. I would greatly appreciate your advice. Thank you!