Please check if the microSD card is properly connected and the computer recognized it.
If the microSD card cannot be recognized, use another microSD card reader to rule out the possibility of the microSD card reader being faulty.
Download the BlackVue PC viewer from our official website and install it, OR you can use the Click&Run BlackVue Viewer program saved in the firmware. (SD Card->BlackVue->Application-> PC Viewer for Windows/Mac->BlackVue.exe).
Run the BlackVue Viewer; wait 20~30 seconds until the BlackVue Viewer completes listing up the recordings and try accessing the settings or to formatting the microSD card.
Chris