Requesting App Access
Creating a Software organization requires a GitHub organization.
By default, OAuth App access restrictions are enabled for GitHub organizations. If you do not see your GitHub organization when trying to create Software organization, you will need to request that an organization admin approves the Software application for use in your organization.
You can request access here, or follow this guide: How to request OAuth app access.
An organization admin will then need to approve the request: How to approve app access.
You can read more from GitHub here.