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

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.