Bill and cost management - access denied.

I've logged into AWS console using my root user account (by clicking the 'Root user' radio button when logging in.

When I go to the Billing and Cost Management home screen it shows 'Access denied' to a number of cost fields.

The documents I've found all talk about adding permission to the IAM user but nothing about the root user.

My assumption is that the root user has access to everything.

I'm seeing the following message at the top of the page (despite this not being the first time I've accessed this screen):

We’re preparing your cost and usage data. This process can take up to 24 hours after you first visit the Billing and Cost Management console. In the meantime, you can view bills, make payments, and manage your preferences and settings. Once your data is ready, you can view cost breakdowns, forecasted costs, savings opportunities, and more on this page. To learn more about AWS Cloud Financial Management, visit the Getting started page.