How to fix Nintendo Switch can't detect Micro SD card.

1. Please check if the Micro SD card is compatible with Switch. If it is compatible,
    please try to power off Switch first, then removing and reinserting the card to
    make sure if it can be detected.

2. Please check for any dirt or debris in Micro SD slot and try to clean it

3. To be sure to perform a system update if the memory card is Micro SDXC type. 
    Here are steps about how to update Nintendo Switch console

※ Before updating, please make sure that your switch is connected to the Internet 

          - Go to the Home Menu and select System Settings
          - Scroll down the System Setting menu and select System.
          - Select System update, to start the system update process.

 If  you insert the card without updating system, it will pop up the screen as below:

            Select System update, to start the system update process.

       4. To format a Micro SD card, here are steps below:
           
           - Go to the Home Menu and select System settings.

           - Scroll down the System Setting menu and select System.

           - Select  Formatting Options

           - Select  Format microSD card, then select Continue

           - Select  Format The console may restart.

          ※ Please be sure to back up information on a computer before formatting.

          ※To ensure proper use, please be sure to shut off the Switch console before
              removing or inserting the a micro SD card.