In case your iphone touch screen is not working, there might be a number of reasons. In some cases the problem occurs because of a temporary software glitch or the presence of screen protectors that disrupt touch sensitivity, or even because of water on the screen. The first step would be to restart the device followed by the removal of any screen protection to verify whether it enhances responsiveness. Provided the problem persists, it may be a hardware problem, like a damaged digitizer or internal component. In this instance, it would be advisable to consult a skilled phone repairer to examine and repair the screen accordingly.