The feature only works when hearing loss is mild (26–40 dBHL) or moderate (41–60 dBHL). We had to repeat the test a few times to get it in the range and enable it.

https://support.apple.com/en-in/120991

Thanks. Any tips on how to do this while keeping the hearing profile as close to reality as possible?

Thanks gmemstr :)

They don't accept passport as a valid government issued proof. It might be automated. Contacting support takes days.