You need to change Z-Index for the Reward Gleam:
1. Go to the Campaign Editor tab
2. Switch to 'HTML/CSS' Editor
3. Click on Extra
4. Expand Gleam Reward Integration CSS
5. Change Z-Index to a higher value (if the Gleam is shown behind any elements), or lower value (if the widget overlaps any elements)
6. Collapse the popup and save changes.