Hi Whalebone & Greenstone!
Thanks for reaching out to us!
We don´t currently have staging.wpengine.com in our whitelist for development sites. But we’re reviewing how this works, so it may be more flexible in the future.
For the moment, you can have your license on your dev site during development and then move it when you are ready to go live. If you need updates on the dev site, you can always move the license again or do a manual update with a latest version from your account’s downloads page.
You can read all about development sites and licenses in this article.
Let me know if you have any further questions.
Best!
Victor