I am doing example "E-Cooling of a Printed Circuit Board" and i wanted to change definition of chips. I wanted to change them from heat source to two-resistor. What I did- i went to physics domain and I picked box "E-cooling" next to chips row.
 

After that i changed the definition in volumne heat source like shown below
 

when i want to run simulation i have the following error.

 

Can someone help me?