MX5 key issue

Any ideas why my spare (and “copy” – i.e. not original, but came with the car) 1989 Eunos key works perfectly except will not open the boot?

Not sure if this applies to the MX5, but many cars, in particular those exported to the US came with Valet keys,keys that would work door/ignition but not boot or glove box, allowed you in US fashion to hand over car to Valet to park, but ptotect your goodies in the boot/glove box

I didn’t think hairdressers would need to use the boot?

is it only the spare that has this problem?

there is a brilliant garage section on the us miata site (google miata garage) your question should be answered there