When you select a database in the Azure Database portal and select the "Configure" tab, you have two options available:
If you press "New Database", you receive the error: "Could not find any bacpac files in the specified storage account."
My initial suspicion was that this button re-uses inputs from the "automated export" section that are only available if you first configure automated export, but even with the tab open, it does some form of scan and reports that it can't find bacpac files (I have 20+ on the storage account in question that were generated from the automated export). This seems to run counter to the help text on the button that says I can use any of my existing exports.
This button is also somewhat confusing. I expected it to work as a Restore button, since it is present inside the configuration tab of an existing database, but the wording of the button and the help text indicate it will create a brand new database.
The fact that the button doesn't work seems to be a straightforward bug, the rest is either a usability bug or a feature request to not be confusing, depending on how you manage these things.