Pls help me with ansoft designer, thanks

I build a low pass filter in ansoft designer, but when I try to analyze the circuit, an error message like below showed up:

Error: no circuit elements to analyze.

There are several circuit elements in the circuit model, like capacitors, inductors, transmission lines, microstrip Tees and ports. Why the designer said that there are no circuit elements?

Did anyone ever encounter this kind of error? What causes this error message and how can I solve it?

Thanks and best regard for your help!

This may happen if you have multiple designs in the same project. While viewing one design (schematic) you are trying to solve the other design (which is empty)

Itai