Vuforia AR cant see the object on tracker.

hello i am using windoows 8.1 and i am trying to make some augmented reality test.

i activate license key and i can see my camera on play mode, however my camera doesn't track my marker. i tried t$$anonymous$$s program on 3 diffrent pc but it didnt work aswell. also my database is activated and my tracker have 5 star on vuforia developer panel. i wonder if its about windows 8.1. any suggestions?

thanks for your time.