Sentry accounts are deactivated after 24 hours and fully deleted after 30 days.

If the old account is still within this period, you will need to wait for the process to complete.

If you need to speed up the process, request reactivation of the old account by logging in to the old account here first: https://sentry.io/auth/login/

Then remove the email address as the primary here: https://sentry.io/settings/account/emails/ or if you're attempting to create an organization do so once logged in here: https://sentry.io/organizations/new/