total energy and loss in piezo model

Hello,

I'm trying to determine the quality factor in a MEMS piezo resonator. But, I'm having difficulty calculating the total energy and loss. The piezo interface comes with W_tot and Q_h,tot already defined as pzd.W_int and pzd.Qh_int, respectively. But COMSOL tells me these are unknown variables. How else can I define the total energy and loss? I haven't been able to hit on the right way to do it.

Thanks so much.
Kamala