need help getting custom map to work on my Fenix 6X Pro

I have seen a post saying that custom maps work on a Fenix 6x Pro

I have watched and read loads of tutorials on how to make them using Google Earth and a .jpg image

when I view the KMZ file in Base Camp, it all looks good, it's sends to the Fenix 6, I can see it in the /custommaps/ folder
and I can see it in the map config settings list

but the KMZ map does not display on the screen

anyone, got any ideas on what I might be doing wrong.
anyone got a KMZ file that they know works, so I can test the watch and play with.

thanks