At this moment, Enterprise subscriptions in instances that were migrated to the improved Atlassian billing experience aren't displayed when accessing the billing preview from the site level. 

Steps to Reproduce

1. Access Jira or Confluence. 
2. Click on the cog icon -> Billing

You should access a page that has these URL patterns: 

https://admin.atlassian.com/s/<SITE_ID>/billing-preview?referrerName=JIRA 

https://admin.atlassian.com/s/537f930a-a47c-4025-a9f0-f0d991be4eea/billing-preview?referrerName=conf

Free, standard, and premium subscriptions are still displayed, the behavior only affects Enterprise.

This limitation isn't present in instances that haven't been migrated yet, Enterprise subscriptions are displayed on those.

Suggestion

Display Enterprise subscriptions at the site level so that site administrators can verify the current usage and contact their billing admins if necessary. 

Workaround

The org administrator can see the licenses at the Org level, it's necessary to contact them to verify the current usage and clarify anything related to licensing.