As I was updating Windows the other day, I received a message that the update cannot continue because additional space was necessary.

Of course my SD card contained that space, but it was gone! Both Windows explorer and Disk management showed nothing!

In the Device Manager my SD card appeared with an exclamation mark, which meant that something was wrong. I tried to update the driver, even uninstalled and reinstalled it, but no joy!

As it was always the case with Windows, a restart would fix things, and it did even this time. Just restarting Windows made my SD card appear again and I was able to continue Windows update.