Thread: Nuvi 58LMT "can't unlock maps".

OK rearranged the SD card and I get the same error. If I don't have the SD card inserted no error.

The D4* files look like they're the FourSquare database. If I click on the "FourSquare" icon in Apps it displays various entries with the SD card inserted but nothing without it. So it seems it is unlocking that fine just not the main map.

I uploaded a garmindevice.xml file. That's a freshly created one. I deleted the original (but backed it up) so it could recreate it in case that helped.

Update. There's a file 844474241.gma in the .System folder with a 2016 date on it. If I delete that the error message changes to "cannot authenticate maps". I've put that file back and now get "cannot unlock maps" again.

Originally Posted by stevex

I've copied the newly created files from the device, SD and older back up and compared. The large *.img files are identical (same hash) but the .gma/.unl don't match. Presumably that's expected?

Yes, they're uniquely recreated.

I am wondering if the unlock algorithm changed in some way that's incompatible with older devices: this one is from 2017.

No, that's not it. I've got much older LM devices which are still offered current maps by the Garmin server.

If there are any diagnostics or other things I can try let me know. I'm pretty tech savvy but a noob when it comes to Garmin internals

Garman_Nuvi will examine your uploaded XML file for any irregularities but meanwhile try as i've suggested below if you want.

Originally Posted by stevex

.............
Update. There's a file 844474241.gma in the .System folder with a 2016 date on it. If I delete that the error message changes to "cannot authenticate maps". I've put that file back and now get "cannot unlock maps" again.

Remove that old GMA file along with the detail map and its associated UNL & GMA and re-connect to GarminExpress again. If you still have the problem without that 844474241.gma, then:

• Make yet another full backup
• Reformat the internal memory using only [Only registered and activated users can see links. ] with suggested settings;
• Create a Garmin root folder and connect to GE to get it updated;
• You might have to also add some Voice, Keyboard and Text folders if it won't boot with only a Garmin folder onboard but try first just with a Garmin root folder, without or with an old or empty GarminDevice.xml in it.

PS: Also clear it's non-vol memory after it boots but BEFORE reconnecting to GE. [Only registered and activated users can see links. ]. Method is the same as for nuvi 2/3xxx detailed in that post.

I did check your garmindevice.xml and the are nothing that stands out.
The garmindevice.xml show the UK & ROI installed as the gmapprom.img
You might be onto something with the unlock codes ,I'm just running some tests at the moment...........

OK, it appears the .unl codes Garmin Express is creating for UK & ROI do not have the correct product number of the map,and the Foursquare .img has the correct one.

Spoiler: Image

Check your PM.
I've uploaded Full Europe with unlock files that are valid for your device to put on your SD card

Yes i tend to agree that this device is getting shafted by Garmin's server for some weird reason. The message "Cannot authenticate maps" is related to a missing or inappropriate GMA file. A problem with unlocking is what invokes the "Cannot unlock maps" message. Problem is that we can parse an UNL file with [Only registered and activated users can see links. ] and even create an unlock code with JetMouse for a detail map to be used on a specific device without GMA in its firmware, but we're unable to read, replicate or spoof GMA files. You can use InfoUC to easily check that the UNL code they've now supplied is for the right map (FID and Product) and for your nuvi 58 (UID). (*See edit below*).

I think it's a fair question to ask Garmin support why the heck they're supplying your device with invalid files. The service desk drones likely won't be able to answer sensibly and will just reach into the box beside them to grab a kitten to strangle instead when you ask for your ticket to be escalated to someone who actually can fix this for you. I know for certain that there are in fact very knowledgeable ppl in Garmin but you'd be lucky to get one first-up answering the support lines and you'd need to be very persistent to get put thru to one.

If you don't wish to inflict the torture on yourself of waiting endlessly on the phone to them, we can copy and then erase the device's nonvol region to see if that clears the problem. Let's know if you want to try that next.

*EDIT: Ah! I see GN has done that for you and it seems the UNL code is indeed invalid. Try recreating the UNL with [Only registered and activated users can see links. ] and replace the one supplied by GE.