There are three things in Snapchat:
- A snap is an image or photo of a moment
- Series of snap are mostly photos of the same event
- A Snapchat story is the video clip of the event or moment
If you have a story then to resolve a black screen error in Snapchat you would have to wait for 24 hours because a story expires in 24 hours and if you have a snap then go into the settings > conversation and delete the snap which is having the issue.
After following the delete snap process you should restart the Snapchat app.