Summary

Sprint is already started, however Sprint Health Gadget does not display Overall sprint progress and Assignees in Sprint. Sometimes it is also possible the gadget is not considering all the issues in the sprint and  % Work Completed on the Sprint Health Gadget shows wrong value. 

Environment

Jira Cloud 

Solution

To troubleshoot any such issues we can check the following 

• Check the board configuration, make sure there are no unmapped statues. In addition check if the columns status are mapped correctly. Done status should be mapped to last column. 
• Jump to Board -> Configure Board -> Estimation section in order to see what estimation statistic is in use for this board. This estimation statistic plays a big part in regards to how that sprint health gadget is displaying data for both the graph and the work completed percentage.
• Check for any duplicate fields. For example if the estimation is based on Story points, make sure there are no duplicate field with the same name. 
• Run the board JQL and verify the issues this JQL is returning. It is possible that the Sprint is having issues from multiple projects and board filter is not pulling these issues.