SYMPTOM:
The tooltip works fine for general document graph chart, however after maximizing the chart (icon highlighted on below screen shot), the tooltip not working, it does not show anything when hovering over the chart.

CAUSE:
It's an known issue on Strategy Web 10.4.
ACTION:
The issue has been now and fix in Strategy 10.4.2 and latest version 10.6.
The Strategy Internal Reference Number for the issue discussed in this technical note is DE49499.