Custom dashboard with widget "Alert List" automatically refreshes per interval for all options of "Group by" except "None".
Categorization under "Group by" folds all of the listed alerts under category except for "None" which makes it easier to view recent alerts. However, option "None" does not refresh automatically whereas manual refresh works.
Aria Operation 8.16.1
API request triggers automatically for widget "Alert List" per interval for all options of "Group by" except "None".
Issue has been identified in the Aria operations version 8.16/8.16.1 and is fixed in 8.17.1.
Please refer to below KB article for more information on [Dashboards: Alert List] Dashboard created with the "Alert List" widget is not refreshed automatically for "Group by: None". - VMware Aria Operations 8.17.1
If the custom dashboard is a shared dashboard, It will refresh with time interval of 5 minutes by default and any refresh interval set <=5 minutes will be ignored as it is by design to reduce the sudden load on the system.