Lost an expansion

I bought GSB a few months ago, on Steam. I got the complete pack, which at the time included the Parasite expansion. ( I distintly remember playing as parasites at least once).

I installed GSB on my new laptop today, and the parasite expansion is gone…I can’t play them. And when I checked Steam, the complete pack no longer includes the parasite expansion.

Is this a steam problem, has it removed my access because it no longer sells the parasites in the complete pack? Why is it retroactive?

Thanks for any help you can provide,