Thanks for your quick reply, @kelshaer .
Have you tried the troubleshooting steps to add Shopify’s mailer addresses to your safe sender list as I suggested yet?
Also, can you please try to change the email address associated with the staff account you are using? Preferably to an email address that is not associated with a custom domain. This can help us determine if the download email is not firing correctly, or if there is an issue with the receiving email address.
Please let me know.