The times I have seen that is when I disconnect from the library without the library being open or when copying a library. The fix for me has been to delete the function from the library, save the library, and then add the VI back into it.
Class or library membership is a two-way information. The library / Class must know of the VI and the VI must knof of the library / class.
If either of these two links is missing, weird things can happen. I get this after LabVIEW IDE crashes (where I have saved a member VI but not the class before the crash).
So, this answer is not particularly helpful. What did you do to fix this? The way a class knows that a method is a member is through the .lvclass file (an xml file). If it is present in the .lvclass file, then the class would seem to be saying that it is a member. How does a method know that it is a member class? Is there a setting in the class method?
What did you do to fix this?
Did you not read my first post? The fix for me has been to delete the function from the library, save the library, and then add the VI back into it.
I believe this is what I ultimately did. Would be nice to understand why this happens as it is unique to LV.