If it’s a one-off, it could just be an anomaly. Maybe for some reason, fewer people looked at stories yesterday.
If it becomes a pattern, maybe try using some easy engagement tools in your stories like polls. The extra engagement should push your stories to the front of people’s queues, if they have engaged with them.
Otherwise, try taking a break for 24 hours. People have said this helps to reset, though I don’t know if this is true.
Also, if it becomes a pattern, examine if your stories are still doing what your followers want them to do (entertain, educate, engage, etc.)