Time Line always honors dependencies on tasks that haven't started yet (Percent Complete = 0). This means that a task will be delayed at least until a predecessor's end date has passed (on a standard dependency). Delay on a Fixed task will be displayed in the Gantt View, if the 'Delay Lines' option is turned on in the Format, Active Window, Time Scale form. An ASAP task will also display visible delay if delayed by Resource Leveling, or if it has been delayed by a predecessor that has been delayed by Resource Leveling.
To see if a predecessor is causing the task to delay, select the task and open the Timing Info Box. This info box lists all predecessors of the selected task. Now click on the left edge of the 'Commands' pull down and select 'Controlling'. The 'Controlling Factors' box will name a specific predecessor task, if it has delayed the current task.