Calculating the absorption coefficient in CST ?

Hello everyone
I simulated the structure with CST and since my structure is periodic in the direction of x and y, I used the floquet port or plan wave.
I want to derive absorption, transmission and reflection coefficients.
If I use the, Calculate Reflectance Transmittance and Absorbance in optical menu in template based post-processing, the following Error appears:
Error in evaluating define function:
"Please define at least one port
How can I resolve this problem?"
Pleas help me

Error seems to suggest there is no port defined in your simulation? How did you assign the ports?

Does the error only occur if you use TBPP? I don't think that's the case, but I would look at how the port is defined