In my laptop, when I connected a memory card to the card reader of the laptop, sometime it was detected. sometime not detected.
I tried other memory card, it was still the same problem. I thought the laptops's memory card reader was damaged.
It turns out the memory card is not damaged
The problem is solved. In the BIOS setting of my laptop, there is an option named Card Reader Power Saving, I changed it from Enable to Disable.
The memory card is always detected now.
Maybe you have the same problem, and has card reader power saving setting in the computer/laptop's BIOS setting, you can try.