A glace at the campaign file tells me the following:
The condition for advancing from sm1-09a to sm1-10a is a) the Taranis having arrived and b) the Taranis never having been destroyed.
This is governed by two events in the mission:
- "Shivans arrives" which works of has-arrived-delay 0 "Taranis"; and referenced via a previous-event-true
- "Taranis dead" which works of is-destroyed-delay 0 "Taranis"; and referenced via not and previous-event-true
The Taranis' departure - which would definitively turn "Taranis dead" false - is tied to the destruction of Ramses by is-destroyed-delay 8 "Ramses".
As far as the pure events are concerned everythings seems to be in order (sm1-09a is a mess in other regards but that shouldn't impact function).