Under the properties for my Civil Cell it says "Valid for Placement = No". What does this mean?
The user does not control this setting. There are instances when changes made to a civil cell can render it invalid. When that occurs, the Valid for Placement setting will change from "Yes" to "No". For example, if a linear template is applied to the civil cell, any changes that are made to the linear template after the civil cell is created will render the civil cell invalid. Even something as simple as changing the name of a feature in the linear template can result in an invalid civil cell.
The solution is to drop the civil cell and recreate it. This will restore the Valid for Placement setting to "Yes".