I had the same problem before, my SD card not reading correctly, and the data lost. Maybe your card is inflected by a virus. Try the following steps:
Open Run dialogue by pressing “Windows” + “R” at the same time.
Open Disk Management by inputting "diskmgmt.msc."
Find the SD card, right-click the partition on it, then select"Change Drive Letter and Path…".
Assign the drive letter of your SD card by clicking "Add" in the pop-up window.
If it doesn' t work, the data in your SD card may lose.
Luckily, I solved it by using Bitwar. Maybe you can try it.