How do I get Genmoji feature on my MacBook Air?

How do I get the new people Genmoji to show emotion. For instance, if I ask for "Julie crying" it just gives me a standard face based on my photo of Julie. Likewise for any emotion I ask for e.g. angry, happy, sad - every time I just get the standard face with no emotion displayed at all. Does anyone know how to show emotion on their genmoji without actually having to just use the standard yellow face emoji? Thanks. I am in the UK btw.

[Re-Titled by Moderator]