COMSOL Error Message

Hi

I've been problems with COMSOL in Plasma Module

The following feature has encountered a problem:

"The source selection for the operator intpot1 must be nonempty. Error in multiphysics compilation.
- Feature: Compile Equation : Time Dependent (Sol1/st1)
- Error: The source selection for the operator intpot1 must be nonempty"

Would you mind to help me?

Thanks you very much

Natthawut