Updating a Project Task from the "Closed" state to "Work In Progress" does not set the Project back to "Work In Progress".

The error message below is shown:

'Updating project state from Closed to Work In Progress, Pending or Open is not allowed. Update existing project task state or add a new task to reopen project.'.

This error comes from the "AjaxProjectUtil" Script Include. The error appears when the Project's Active field is set to false.
Whenever the Project Tasks were reopened, the State value would not properly update the Project and the Active field would remain false.

This was happening due to a customized "PlannedTaskUtilsV2" Script Include.

To revert the "PlannedTaskUtilsV2" Script Include, follow the steps below.

NEXT STEPS:

1. Navigate to System Definition > Script Includes
2. In the "Name" column search for "PlannedTaskUtilsV2" and go to the record
3. In the Versions related list, open the record with the latest Source of "System Upgrades: glide-LATEST_RELEASE..."
4. In the related links section, select "Revert to this version"
5. Select OK when prompted