There are a few reasons on why this may happen:
- Ran out of audiences due to impression/frequency caps.
- Due to our pacing algorithm, which is designed to spend your budget as evenly over time as possible so that your budget does not run out. If your campaign had a strong start, the algorithm corrects for this by limiting the volume of impressions served daily. You are welcome to increase budget or decrease the flight dates to speed up impressions served.