Hi

If you are using a type that is defined in .ino code as arguments to a method you need to manually add a prototype in the correct location. 

Historically for arduino, types have been defined in header files because it wasn't possible for the ide to automatically add the prootype in a location between the definition of the type and the method that used it in its signature.

A change last year in the arduino ide added more intelligence but its a complicated change for visual micro due to the needs of the injected debugger code.

It will be implemented shortly so for now add the prototype yourself

//type defined here
struct mytype

//method prototype here (between the two with exact same signature
void mymethod(mytype arg1);


//method here
void mymethod(mytype arg1)
{
}

If this is not the problem then please email your .ino file(s)