The problem of TKLCAF.dll

I want to initialize the TDocStd_Application :

      Handle(TDocStd_Application) aApp = new TDocStd_Application();

However, the compiler prompts that it can't load the symbol from TKLCAF.dll. Other class can be used normally, such as TDF_Label, Tdocstd_Document. My occt version is 7.40 and the compiler I used is vs2019 in window10. Why is this a problem? How can I solve it?