Failed to find consistant initial values. in Electric Current simulation

Hello Everyone~

I have question and need your help.

In the file I attached, there is simple model comprised of materials, Air, Liver tissue, Blood, Electrodes and Troca base.

When I define block1, 2 and 3 as the material property of Liver tissue, the simulation operates well.

However, if I change the material property, (block1 to blood and block2 to air)

The simulation is stopped at initial step and following message appears in error stem of Time-Dependent Solver 1.

"Failed to find consistent initial values.
Segregated group X1

Singular matrix.

There are 2169 void equations (empty rows in matrix) for the variable mod1.V
at coordinates: (0,0.0239887,0.0605475), (0.000422692,0.0237896,0.0607071), (0.000417261,0.0241921,0.0608184), (0.000343571,0.0239178,0.0603889), (0,0.025,0.06115), ...
and similarly for the degrees of freedom (empty columns in matrix)"

I tried to fix the problem many times, but i couldn't resolve the problem.

In my opinion, the problem is in Electric Current interface because if I enable heat transfer interface only, the simulation operates well.

Can you tell me how to solve this problem or what is the wrong?

Thank you for reading~:)