first of all sorry for the long post. I have a nuvi 2455 that i have flashed it seemed to go perfectly but says can not validate map product. this is what i have done. downloaded the latest firmware version 820.gcd this was already installed on the nuvi. my details from the xml file coincide with this below
HWID: 1371 | SWVS: 820 | MAP: Yes | GMA: Yes | MSV: --- | GVS: Yes | File: nuvi24x5and25x5_GCDFile__820.gcd
Next i downloaded all the files in the universal patcher thread.
next , opened the firmware patcher.exe and dropped the 820.gcd file into it for conversion and saved the converted resulting file.
then i opened the rgn tool and droped the converted file into it and saved the converted file as 137101000820.rgn
I then removed the old 820.gcd from the nuvi and switched off.
i then opened the updater .exe and loaded the .rgn file into it selected usb and connected the nuvi and put it into preboot mode and when it was visable in in updater.exe clicked ok.
The unit went through the flashing procedure and confirmed all done ok. switched off and back on with no problems.
i had already downloaded the City Navigator Europe NTU 2016.30 torrent file. now this is where i may have gone wrong, i took the locked .img file out of the torrent and unlocked it with gimgunlock+mapsig and then drag and dropped it onto an sd card into a folder named garmin and when done changed the files name to gmapsupp.2 and then put the sd card into the nuvi and thats about where i am at, getting the can not validate map product.

Have i done all the above correctly. Many thanks in advance Lee