I can create a database and select a user from the drop down on MyDomain.com When I attempt to create a database in servr1.MyDomain.com the database user: drop down is empty and says "NO matches found" I can still crate the database but it is not useful without a user associated with it. Server and site look OK. Site Auto Subdomain does not seem to matter.
The database user must be created for the same client that owns the website. If the client and website owner match, then the database user shows up in the dropdown.