Footing material missing.
Every footing must have a material associated for each of its components that describes the material properties of that footing component.
For footings placed by the Footing command, this can happen if the catalog is edited to remove the specified material after the footing is placed.
Any reports related to the material properties may fail. For example, if no material is found, the weight is calculated using the approximate density of concrete (2400 kg/m3).
What You Should Do
Open the model.
Select the footing, and then click Properties on the ribbon.
Select the Occurrence tab.
In the Material box, choose a valid type.
Apply the properties, and then exit the dialog box.
If the problem is not resolved, make sure that the custom content is setting the material on the footing for each of its components, or directly on the footing component for the assembly footing type.