File Server

Hello, I just recently discovered file server sharing on my iPad, I watched a tutorial and was able to connect my iPad to my Windows PC. (Windows SSD) I was able to add and delete files, images, and so on between the two devices. However, when I used an SDXC (SD card adapter) and USB (USB and USB sdcard reader) as file servers, the only thing I couldn't do on the iPad side is to import any kind of media FROM the iPad, every time i do, it always says INVALID ARGUMENT. But i was able to save, add or delete files there as normal. Everything is fine on the Windows PC side.