How come the scheduled dashboard is timing out?
When a scheduled dashboard delivery takes longer than 20 minutes to process, it times out. This happens if the dashboard contains large or complex reports.
Scheduled dashboards are made out of multiple reports executed in parallel. The schedule fails if one or more of the reports takes more than 8 minutes to execute. If a report takes longer than 8 minutes, Explore attempts to execute it a second time. If it fails the second time, a timeout notification email is sent to the owner of the schedule.
To avoid this, ensure your dashboard contains less complex reports and data to load.
For more information, see the article: Scheduling dashboard deliveries