If you take the photo in automatic mode without flash, you should be able to use the Duo effects. A way to test if the secondary camera is working is to launch the camera app, let it focus on an item a few feet away, and put your finger in front of the secondary camera. You should get a message stating "Duo camera is blocked, please make sure all lenses are uncovered". If you do not get this message, then there may be an issue with the secondary camera or the software. If you DO get the message, and still cannot use the Duo effects, then you may have a processing software issue. Eithery way, you should call HTC support. Be forewarned that they may ask you to reset your phone, so back it up first.