Task status and % Complete cannot be changed and there is a mismatch in the two values

Document ID : KB000103484
Last Modified Date : 18/07/2018
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Issue:
We have an issue with some tasks not being able to be edited to be set to "Completed" or the % complete is set to 100% but the status still says "Started" and cannot be edited to "Completed" while other tasks are not facing this issue. 
Cause:
  1. The issue with task status and % Complete not being editable can happen if the % Complete Calculation on the Project is set to Effort and there are any non Labor Resources assigned to the task.
  2. Additionally, the issue with task status changes not saving even if the % Complete calculation of the project is set to Manual can be due to there being ETC left on the task. 
Resolution:
For the % Complete Calculation Method of Effort, non labor resources are not included in the calculations. In order for the task % Complete and Statuses to be able to changed, the project % complete calculation method would need to be Duration or Manual. Note: It is not recommended to change a % Complete Calculation Method of a project once it's been set as this can impact the task data. 

Note: Even if the % Complete Calculation Method of the project is set to Manual, in order to be able to save a task status of Completed, there must be 0 ETCs on the task. See KB000103580 for an error you can see on the Gantt when trying to update a task with ETCs greater than 0. 
Additional Information:
Reference % Complete Calculation Method section of the Create Projects, Teams, and Tasks documentation for details on the differences in the three types of % Complete Calculation Methods.