Can't get Gantt chart view


I created a sheet in Grid view for projects I'm managing. It has start and finish date columns, along with task names, etc. I've done some copying and pasting to put tasks in there. When I click on gantt view, only a handful of tasks show up on the gantt chart. What am I doing wrong? I've looked at the properties and don't see anything amiss. Here's a screen shot of the sheet.