I just did an Up2Date on my production Astaro from 7.404 to 7.405, and learned that the button can be made to appear if one simply clicks on the Astaro refresh symbol at the upper-right of WebAdmin. Perhaps that will clue the developers to an easy fix.
Cheers - Bob
Sophos UTM Community Moderator Sophos Certified Architect - UTM Sophos Certified Engineer - XG Gold Solution Partner since 2005