The project Status does not change from Complete back to Current.
The cause of this problem is the Completion Mode setting on your project. If a project’s Completion Mode is set to Automatic, then the project will automatically change the status from Current to Complete after all tasks and issues are completed and the project’s percent complete bar is 100%. In this case, manually changing the status of the project from Complete back to Current is not possible.
If a project’s Completion Mode is set to Manual, then the project status can be changed from Complete back to Current anytime.
To update a project’s completion mode to Manual:
Go to the project you want to update.
Click the More icon to the right of the project name, then click Edit.
Click Project Settings.
Locate the Completion Mode drop-down menu, and select Manual.
Click Save .