New Simulink error message in Matlab R2020b?

I'm getting the following error when I try to execute the Impedance Measurement tool from the powergui bloc:

" Error evaluating 'MaskDialog' callback of PSB option menu block block (mask) 'slx_file_name/ powergui'. Callback string is 'close_system(gcb) power_zmeter(bdroot(gcb),gcb)'

Dot indexing is not supported for variables of this type. "

Where "slx_file_name" is the name of the file containing my Simulink model.

This is a model I'm using for many years and never got any error message of this kind with previous versions of Matlab.

[Jean-Jacques]

Does any one knows what is "dot indexing"?

[Fangjun Jiang]

Many times it refers to structure or properties of an object, e.g.

a.b=1;
S=Simulink.Signal;
S.Dimensions