This was an error encountered in the previous versions of Snapchat. I searched the web for common fixes, but there aren't many. One thing that was said to fix the black screen by activating the camera rotation feature. To do this, activate the phone rotation feature, then rotate the camera while the camera is activated, then rotate it back to initial position and the image should appears.
Additionally, reinstall the software and activate your account again. If you have an outdated version, it will update to the latest one.