I have just updated my Nuvi 57LM to the latest version of City Navigator NTU 2020.20 through Garmin Express.

I expected this latest map to also be made available to the Nuvi 58LMT which I also own, but there is no update showing within Garmin Express.
This unit updated perfectly well a couple of months ago when the last version 2020.10 became available.

Is there any obvious reason why one Nuvi would show the update but not the other?

I know it's not a major issue, but I wonder if anyone might have any ideas why?

Thanks for any replies.