Why can't I manage people or business billing?
Some settings require ownership even when you can manage accounting settings.
People, business billing, business profile and email sending are owner-only settings. The Manage business settings, roles & permissions permission does not make you an owner. An approved firm accountant also does not become the business owner through their assignment. Ask an owner to make the change or review your role. Find and save a setting explains which pages use ownership and which use a task permission.