In order to let the app access your camera you’ll need to enable it in your privacy settings. However, depending on which iOS you have installed, the procedure differs slightly.
The easiest way to do it is to go to Settings > Reset > Reset Location & Privacy. This won’t delete anything form your device, only resetting the access your apps have to different features. Next time you open the Toca Hair Salon Me app, make sure to answer yes on all the questions that pop up and now you should be good to go!
Oh, what is also good to know is that resetting this will reset the device features on all of your apps, so next time you open another app you’ll have to give it access again. It will ask the question automatically so there will be no extra struggle for you.