I have nuvi model 1440/1490/760 and map of Aus Nz showing fine on the micro sd card.

When try it on other nuvi models i.e 58LM it cannot read the data, say its corrupt. Does anyone know what the problem is?

Have you patched this 58LM?

How do I patched it? I dont have access to the 58LM.

Basically I sent it to someone from another city so I have no access to it.

So the problem is to the 58LM it should be patch his firmware in order to recognize other unlocked files, if your files are unlocked!
In fact what exactly need is this 58LM to recognize also your maps is n it?

Thank for your response.

Are you saying certain model cannot read the map and need a firmware update in order to see it? While my 3 of my nuvi are able to show?

I got the Aus NZ 2017.20 map from this forum.

Standard Uk or Europe Map internally on the nuvi memory, the aus map is on an micro sd

Yes exactly ! The new especially devices like 58LM have new special locking protections so even that the maps are already unlocked they cannot be recognised from the device unless the firmware is patched. I can help to do it but you have to have access to the device of course.
We need the GUPDATE.GCD file from the device if this does not exist on the device you can again redownload with webupdate of Garmin if again cannot find it i need at least to know and to be sure about the HWID of this device before send you a patched firmware and explain you how to uploaded.

Alright so garmin naturally beefed up the security protection to prevent people like us doing this I see.

Do you know from what nuvi series this security kicks in?

When I have access to a similar device which requires a firmware update I will enlist you help, thanks.