Failed to find a solution. The relative error (35) is greater than the relative tolerance. Returned solution is not converged

hi, im writing this mail because im stuck with my thesis simulation. this happened when i change the value of the electrical conductivity for silicon. i change for 1.6 e-3 s/m instead 1e-12 that had before ( the simulation works with this parameter).

i dont have any idea what can be wrong because the real parameter is 1.6e-3 s/m and the error that comsol is telling me each time i run the simulation is Failed to find a solution.
The relative error (46) is greater than the relative tolerance.
Returned solution is not converged.

another doubt is that i need to obtain the voltage on the perpendicular contacts. i put the boundaries like floating potential and i did a graph using thedifference of both contacts but i would make sure if im doing right.

i really appreciate any help to solve this problem

thanks