I found something from previous respond from Tom_BPC
1. It seems Task Path highlighting won't work if you have deleted or renamed the three core bar styles: Task, Milestone, and Summary.
Task Path works by adding bar styles, depending on bar styles that are already on the list when the tool is clicked. Thus, when you select "Predecessors" in the Task Path menu:
If a bar style named "Task" already exists, then a new bar style named "Path Predecessor Normal Task" is added near the bottom of the list.
If a bar style named "Milestone" already exists, then a new bar style named "Path Predecessor Milestone Task" is added.
If a bar style named "Summary" already exists, then a new bar style named "Path Predecessor Summary Task" is added.
Project toggles the icon's background to indicate that the tool has been engaged even if no bar styles have been added.
Up to 12 bar styles can be added to the list (three bar styles for each of the four tools.) If the Task, Milestone, and Summary bar styles have all been deleted or renamed, then NO new bar styles will be added, and Task Path won't work.
2. If you are using a different Office language pack, then the default core bar style names may be different. Look for them near the top of the bar styles list in your default (Global.mpt) Gantt Chart view. (If this still doesn't work, then there may be a language-dependent bug.)
3. The other Bar Styles tools - e.g. "Critical Tasks", "Slack", etc. - also add and remove bars, but without the same dependence on current bar names. Maybe this restriction will go away in a future update.
