Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Have you tried turning the Garmin Nuvi device On, after having it Off for a few minutes, with the SD card inserted? that sometimes gets the updates onto the Garmin device automatically.
Let me know if that works, please. Or, if it does not, I will advise you further.