Projected Start Date, Planned Completion Date, and Projected Completion Date not calculating

I have a project with two tasks that are not calculating the Projected Start Date, Planned Completion Date, and Projected Completion Date. Those fields just list N/A. I have checked the start mode (which is set to Start Date) and constraint (which is set to As Soon As Possible). I can't figure out what else I'm missing that might be causing this. Anyone have an idea?