If the files on your SD card are corrupt, we can use some PC tools to try to fix the problem. Here's how to do it.
One of the most convenient ways to share data from one device to another are SD or micro SD cards: in a small space they can store a large amount of data and, at least those of higher "class" (such as UHS Class 1 and 3) are also fast in reading and writing data. For this reason, SD cards are used in electronic devices that require excellent performance in reading and writing, such as smartphones and digital cameras.
Unfortunately, however, even if SD cards are very robust, it can happen that they no longer work because of some hardware problem or file system. If it's a hardware problem (e.g. an electrical connection is broken or the card is bent or broken) there's usually not much you can do. But if the problem is in the file system (i.e. corruption of the stored data) very often you can fix it and get the card working again. To do this, you need to connect the card to a PC or Mac, either by using an external card reader or by inserting it directly into the slot in the computer. Laptops and MacBooks almost always have an SD card reader, for example.
How to repair an SD card on a PC
If you want to repair an SD card on a Windows computer, the first thing you need to do is connect it to the PC. If Windows detects it and assigns it a letter in the drive (C, D or E, the ones found next to a hard drive or external memory in File Explorer), but tells us that it is impossible to access the external memory, then we have hope of making it work using the chkdsk command. First we need to open the command prompt by running it as a system administrator (just use Cortana's search function to start it), otherwise chkdsk won't work.
Then we need to type "chkdsk" followed by the drive letter and the colon. For example, if Windows has assigned the letter "h" to the SD we should type "chkdsk h:" and press enter. If we don't add other parameters to the command, however, chkdsk will only check if there are errors on the memory but it won't repair them. If you write "chkdsk h: /f" instead, where "/f" stands for "fix", then the utility will first look for errors and then try to fix them. If all goes well, then, the SD card will be back to work even though it is always possible that some files on it will no longer be available.
How to repair an SD card on Mac
To try to repair an SD card on Mac we can use Disk Utility. The first thing to do is to open the utility and choose View > Show All Devices, hoping that the card has been detected by the Mac. In this case we just have to select among the external drives the volume associated with the SD card and click the "S.O.S." button. At this point Disk Utility will check the SD card for errors and, if it finds them, it will repair them itself without us having to ask it.