You don't provide the error message so no other user can help since they don't know what it's happening.

Usually, content blocking add-ons have a toolbar button you can use to make an exception for the currently displayed site. If you don't see the button for yours, it's probably on the drop-down list below the puzzle piece. You can pin it to the main part of the toolbar for easier access. See: Manage your extensions using the extensions button in the toolbar.

Does that satisfy Yahoo?