Map update Maserati Ghibli CTP13

Hi all, I have a 2015 Maserati Ghibli that came with CTP16 and has the can't unlock maps error. I've spent hours trawling the internet trying to fix/update the maps but am getting nowhere. Any help is greatly appreciated. Here is what I have done so far.

Inserted USB in car to download map status using update maps option
Inserted USB in PC with Garmin Express installed - it finds CTP16 from USB but when updating I get cannot connect to server error
Downgraded car to CTP13 using CTP13 4.08.rar - success!
Inserted USB in car to download map status using update maps option
Inserted USB in PC with Garmin Express installed - it finds CTP16 from USB but says system is up to date
Downloaded torrent of City Navigator Europe NT 2024.10
Installed BaseCamp - maps are working OK on PC
Created USB image with following directory structure

Garmin\gmap3d.img
Garmin\gmapsupp.img
Garmin\ASR\all files from torrent download directory
Garmin\JCV\D8957030A.jcv
Garmin\JCV\D8958030A.jcv
Garmin\SID\all files from torrent download directory

Inserted USB in car and navigated to update maps option - nothing happens, it just writes another status file
After inserting USB into PC BaseCamp now says my device has CN Europe NT24.10 maps but I still get can't unlock maps on the dash in the car

Any ideas what I am doing wrong? The unit is downgraded to CTP13 and I have working maps on BaseCamp so I think I have all the tools to finish the job. It's just a question of how to build the USB image correcty.

Just to add after inserting the USB into my PC I can switch maps in BaseCamp and use the map from the USB. So the map on the USB is working it's just the unit in the car doesn't see it and won't copy it across.

What happens when you insert USB into the Car unit?

It writes a file garmin.xml to the USB and gives an instruction on screen to insert the USB to a laptop and download the latest maps but, when I insert the USB into my laptop and open Garmin Express it says I am up to date.

Hi, I succesfully update maps with Garmin City Navigator Europe NTU 2025.10 in Maserati Ghibli MY14 with CTP18.
I used files for North region:
gmapsupp.img
gmapdem.img
gmap3d.img
ASR - all
JCV - for north
SID - for north

I had error at validation process so I used three-step process.
First was with only three img files
Second was with only gmapsupp.img and JCV
Third was with only gmapsupp.img and SID and ASR

I copied files direct from City Navigator Europe NTU 2025.10 to USB SANDISK pendrive 3.0.
Try this.