Help with Nuvi

when trying to format a raw micro sd card I forgot nuvi 255w was connected and must have wiped a partition on nuvi instead of sd card.
1 - Now when I start nuvi it boots to nuvi logo and copywrite screen then keeps reebooting over and over to same screen
2 - when I boot with sd card in it boots to select time and select units screen then register your product screen
then warning screen and then No detailed maps found that support routing.The nuvi cannot be used without them..
3 - If I boot holding upper left of screen I get to press dot callibration screen then ok then warning I aggree then loads the where to and view map screen...when I go into tools settings and map there is no map there.
3 - I have a full backup of nuvi on pc and also full backup on sd card but now nuvi will not connect to pc so I
cannot install the backup.
4 - I have tried holding upper right of screen ion volume screen trying to put nuvi into storage mode but nothing happens.
any help

Do not panic read here and fix it

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I have tried this with gcd file from full backup and when I get to updater I chose usb device but garmin is not recognised
so can not proceed.
that is main problem can not get pc to recognise garmin..

Update managed to get gcd file from full backup then make firmware then clicked updater exe ticked usb when garmin appeared pressed ok then got loader loading then loader nuvi 2 series software version 7.80 then software loading then update succsesfull
then goes to garmin logo on screen.
on pc removable disk j appears for about 3 seconds then goes away so still can not see garmin on pc
Update can see it in device manager under garmin devices garmin usb gps, it has a yellow triangle with exclamation mark.

new development have changed gmapprom.img to gmapsupp.img on sd card with full backup then inserted into nuvi and went into loading maps and on garmin map screen I now see the map...have connected to pc and this time connected but only the sd card is seen not the nuvi . loaded partition mini tool partition wizard and it shows sd card as fat 32 there is also an basic drive of 1.82GB whici has unformatted partition of 1.8GB and unallocated partition of 16MB will the basic drive be the nuvi 255w and should I format it?

Please read carefully the document that i have sent you may need to format the device before to start everything.

format partition and now when connected to pc with sd card inserted which contains full backup I get the garmin logo and white box with pc etc below it on garmin screen...but on pc all I can see is the sd card no garmin device so can not copy the full backup to garmin nuvi

Can you tell me your HWID? or even better to send me somewhere your firmware?

is this what you want? 006-B0827-00 taken from backup

Yes just wait !

Download those files

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extract them on an empty SD card put it on the device and reboot
TELL ME WHAT HAPPENED

when done reboot loader flashed on screen for a second then nuvi rebooted and said loading maps then warning agree screen then this screen No detailed maps found that support routing.The nuvi cannot be used without them

So now it can be seen by PC ?

no still can not see it on pc

How you formated ? and was with RMP in fat32?

sorry that is my mistake not formated yet as can not get nuvi to show up in RMP

Update now managed to format as said through RMP

appeared on desktop and transfered full back up over to nuvi removed from pc rebooted but still keeps rebooting at nuvi copyrite screen...
If put blank sd card in and boot holding top left of screen I can get into nuvi but when I look for map voices etc it says there is none...

I can not do the boot holding bottom right of screen does not work only goes to copyrite screen then keeps rebooting.