Adding a 'Custom Bloc' to 'Bloc Library', but missing Classes?

Hi – So, I’m trying to make a Custom Bloc, and when exporting the bloc to the Custom Bloc Library not all Classes show in the list (see attached image for the important missing class).

Any thoughts?

Also, what’s the significance of the ‘Required Bloc Classes’ check box? When this class list was generated, the first check box for the first class in the list, nav-tab .nav-link, was de-selected, but when I click the empty ‘Required Bloc Classes’ check box, it selects that box AND this nav-tab… class gets selected, but when I select this class first the ‘Required Bloc Classes’ check box does not get selected.