The version included with Cubase is the free Halion Sonic 7 player, which includes libraries exclusive to users of Steinberg’s DAWs. I imagine this is what you’re referring to. This content isn’t the same as the paid “Halion Sonic 7 Collection”, and it currently doesn’t qualify for upgrade pricing, unfortunately.
See this topic for a list of licenses which can be upgraded to Halion 7:
Free HALion Sonic 7 (included with Cubase, Dorico...) cannot be upgraded to HALion 7!