Sd card not working

Hey all. I have a question and it's about having a micro SD card. I had a 1tb micro SD card (Sandisk) for emulation purposes. I wanted to swap it out and put it in my Ayn Thor.

I formatted it on my computer. I was able to do it but for some reason, when I copy files onto the SD card. Every time I eject it and put it back into my PC the files disappear and I have to format the SD card again.

Did I have to do something on the steam deck for the SD card to work properly on my PC?

Thank you for your time.