Can't select item filter no matter what

My problem is that when I go into the game and click to select the item filter, which I've already saved in the correct folder, instead of selecting it, it just opens the file as a Notepad file as if I were browsing in my folders outside of PoE, instead of going through the folder through the Path of Exile system. That way, I can't select any item filter at all, because when I click to select it just opens the file instead. I've tried every tip available on the internet to try and solve it, nothing worked. Please help.