simulation – Piezoelectric energy harvesting (cantilever) model using COMSOL Multiphysics 5.6

I have designed a simple Piezoelectric energy harvesting (cantilever) model using COMSOL Multiphysics 5.6 in 3D. It consists of two layers Substrate and Piezo layer.

The problem I’m facing is that I can’t extract an output voltage vs. frequency graph. The graph always appears empty. However, I can obtain the displacement vs. frequency graph result. The issue seems to be with the voltage output.

Additionally, I’ve noticed that my simulation takes hours to complete. I have attached my COMSOL file for your reference.

Thank you!