Cannot authenticate purchased maps

Seems the most likely cause of the issue you are experiencing is that the map was never fully installed, and the licensing codes that authenticate it on device boot were never written to the internal memory as a result. Furthermore, it does appear Garmin servers are having some 'down time'. 

You will have to retry again at a later time so the entire map can be installed correctly.

Maps have been properly installed and worked fine for over a year. 

These messages happened only recently and I havent seen them before, I have update maps and device SW before and never seen error on boot or in Express. 

Hello, when this occurs please try the following steps listed in this article "Cannot Authenticate Maps" Error Message on an Outdoor Handheld. 

Unfortunately, no Garmin device will tell the user WHAT MAP is having the issue.

I also have this problem on my Montana 7x0, with many maps loaded, and there is no way to determine which map is the offender without spending hours removing and reinstalling individual maps.

HORRIBLE execution by Garmin.

Horrible.

Strongly agreed, the message is poorly lacking any useful information and way out of touch with the current product set.

It's been the same simple message for years across all devices despite the ongoing release of devices with increasing capacity for additional maps, correspondingly increasing chances of something going wrong and more complication to manually identify which one.

Needs at least to define which map it has a problem with.