Problem with ofxKeyboard

Hello elllllo~
I would like to ask if anyone has experience with ofxKeyBoard please?
I was trying to run the example on oF v0.9, however, I try (either to type with keypressed or an actual press), the virtual keyboard that is being drawn doesn’t print anything.
As far as I understand the example code, the string letter has been drawn from the addon of ofxKeyboard and hence it means it has been “detected”. And void virtualKeyPressed (string & letter) is only calling the letter being pressed. Hence, I’m not sure why is it not working…

I have also tried running it on oF v0.84 but it failed to run, hence it’s funny that it runs successfully on v0.9 but totally failed on v0.84…

It would be wonderful if anyone who has used it before successfully could tell me the tips to make it work~

Thanks a lot and have a lovely day!

Best Regards,