My nüvi 3590LMT has basically run out of memory, per Garmin Express the base 8GB of memory is 100% full (in reality there is about 4MB remaining); I have purchased an 8GB Class 10 MicroSD card which, while visible from Windows Explorer, was not recognized by Garmin Express. Numerous exchanges with the Garmin Support folks yielded no help. Hoping maybe the issue was the card itself, I purchased a 32GB Class 6 MicroSD card from a different manufacturer and it too has the same issues.
Researching this forum I see numerous complaints of the same issue; some have managed to get them solved (with no apparent solution documented), and others have not. I am currently running North American maps version 8.3 and am running Garmin Express 6.6.
Given the extreme lack of space available on my device, with or without an additional memory card, the device can take upwards of an hour to calculate a simple route, and if I start moving, even at a walk, the GPS lags far behind. On a recent drive to work, with additional memory card, and without a route, the unit refreshed the screen so slowly it was some 15 miles behind when I pulled into my office parking lot.
At this point, the customer service person has given me only one option, pay to upgrade my GPS unit. For my part, I'm trying to figure out why I would invest in another Garmin unit if in a couple of years the software/firmware will render it inoperable like my current unit.
Any help in getting my device to recognize either of my MicroSD cards would be greatly appreciated.