I have tasks with zero total slack and they are not appearing on the critical path (the bar graph is not turning red). I can't figure out why not. Some tasks with zero total slack are showing up but some are not. I've tried to clear the formatting but that didn't fix it. Notice on the screen capture that "DV Build" is not appearing red in the bar chart but the total slack is zero. Any ideas?
The task split (...) color for the DV Build task is red, which indicates that Microsoft Project recognizes that this task is a Critical task. However, you or someone else has applied custom bar formatting to the Gantt bar for this task. You can clearly see the custom bar formatting for this task's Gantt bar since it contains the cross-hatch pattern as well as the blue color.
To resolve this problem, you will need to remove the custom bar formatting for every task in your project. By the way, instead of using the custom bar formatting, I would recommend you use cell background colors to denote tasks of interest.
To remove the custom bar formatting, click the Task tab to display the Task ribbon. In the View section of the ribbon, click the Gantt Chart pick list button and select the Reset to Default item at the bottom of the menu. Click the Yes button in the confirmation dialog. Then click the Format tab to display the Format ribbon and select the Critical Tasks checkbox again.