Gen Registration (Brains) fails despite overlap of series

Dear Slicer community,

I am following tutorial: https://www.slicer.org/w/images/b/ba/NRR-CTgLiverAblation.pdf
to register T1 and T2 liver MRI images. I created mask for both sequences, and the sequences definitively overlap in the 3D space! however, I am getting the same error message as Rewati

General Registration (BRAINS) standard error:

ExceptionObject caught !

itk::ExceptionObject (0xfb3160)
Location: “unknown”
File: /home/kitware/Dashboards/Nightly/Slicer-0-build/ITKv4/Modules/Registration/Metricsv4/include/itkMattesMutualInformationImageToImageMetricv4.hxx
Line: 205
Description: itk::ERROR: MattesMutualInformationImageToImageMetricv4(0xb3c290): Joint PDF summed to zero
General Registration (BRAINS) standard error:

ExceptionObject caught !

I tried multiple initial splines and I am truly getting desperate. I’m using Slicer 4.8 on Ubuntu 16.04. Any help/suggestion is much appreciated. I uploaded the NRRD files and a screenshot from the GUI interface to the following folder: https://www.dropbox.com/sh/ly2rbeyoxe3ja07/AAC1UKMLWrZm_vOEUXAK0dDsa?dl=0

Thank you very much!
Alex