This Class is Missing One or More Methods of an Interface it Implements
From Xojo Documentation
One or more of the methods of the class interface that this class implements could not be found in this class, even though it claims to implement the class interface.
Notes
When you specify the properties of a class in its Properties pane, you can optionally specify a class interface for the class. When you do so, the class must have its own methods of the same names as the names of the methods in this class interface. The matching methods must use the same parameter types and return types as the corresponding method in the class interface.
If you omit one or more of these methods, then you will receive this error. When you attempt a debug build, a dialog box will appear that gives this error message and contains a list of all the methods that the class is required to have.