This means that this CPT code was on your Flow Sheet and marked as performed (lit up in green), and then the Flow Sheet was edited to hide that function. The Flow Sheet will still see all functions marked as performed, even if they are hidden.
To solve: Right-click and Edit Flow Sheet | Check the box next to the function and click OK. This will cause the function to become visible again on the Flow Sheet. On the Flow Sheet, you can now, uncheck the function so that it is greyed out and Validate your charges again to ensure it is not included.
After that, you can edit the Flow Sheet again and hide that function if you like.