If you are in a scenario it might only be available if you research it. It depends on the settings for the scenario. Try opening it in a sandbox park and see if it is still missing . . .
This might be intended. I remember that many community members suggested that new objects and rides which come with DLC's should not be added automatically to existing scenarios from the start. Prior DLC Rides where available from the get-go at every scenario which affects the intended balancing of the missions, especially for custom scenarios so I think frontier has done this to fulfill those requests.
Thanks for the SLV improvements. So close to being able to make launched shuttle loops. Hopefully soon they will implement this into the game.