Once you are now at 9.0.1, you will need to edit the inc/classes/BxDolUpgrader.php again and add /beta/ to the URL like this:
protected $_sUrlVersionCheck = 'https://v.una.io/beta/';
Go back into your Dashboard and check to see if you now see a 10.0.0-B1 is available. If you do not see it, clear your cache and refresh the page.
See more details here https://una.io/page/view-discussion?id=3216