1. Check if the microSD card is properly inserted in the slot

Steps:

1. Disconnect all external storage devices except for the microSD card
2. Switch off your computer and remove the microSD card
3. Clean the contacts of the microSD card and re-insert it in the slot
4. Reboot your computer and check if the card is being recognized

2. Update or reinstall the card reader drivers

Steps:

1. Go to the device manager and locate the card reader driver
2. Right-click on the driver and select update or reinstall as per your requirement and follow the onscreen instructions