We encountered a bug that results in having class controls/indicators/constants to be grayed out in our code. In our case, it was when we changed the PPL that contained the parent of the class.
We created the attached VI Analyzer test to fix this issue if you encounter it.
This test will detect any LabVIEW Class controls, indicators, or constants that are grayed out due to having an invalid default value stored in them. It has an option to reset the value of the object to the default value for the class and save the VI, which should remove the grayness.