If all project tasks are marked 100% complete, what action must be taken to resolve a status update error?

When all project tasks are marked 100% complete, the task status should be updated to "Done" to accurately reflect the project's completion status. This action is necessary because in project management systems like Adobe Workfront, simply marking tasks as 100% complete does not change their official status. The "Done" status is a final designation that signifies that a task has not only been completed but also that the results have been reviewed and accepted as part of the project deliverable.

Updating to "Done" ensures that all stakeholders have a clear and consistent understanding of the project's progress and current status. Additionally, it helps trigger necessary final processes, such as project closure activities and performance metrics evaluation, which would be critical for moving the project towards completion and measuring success.

The other options suggest various issues that might arise within project management workflows, but they do not directly address the core issue of syncing the task status with the completion percentage that has already been indicated. Therefore, confirming the status as "Done" is the primary action needed in this situation.