The cooling network solver solves the coupled continuity, momentum, energy and minor loss equations in the cooling circuits. One or all of these equations is not converging to a zero residual and is giving rise to an incorrect circuit network solution in the circuit with the specified inlet node.
The circuit could possibly be a parallel circuit comprising elements that have very little flow. If this is the case, and the residual is very small (less than 0.1), then the warning can be ignored. This depicts very bad circuit design and it is suggested that the circuit design be changed. Otherwise, there could be a modeling error that is giving rise to this warning.