F4 key not working as a keybind

Hello support,

A long time ago I used F4 as one of my hotbar keybinds. Some time ago it no longer worked, and I resorted to use ` instead.

Just now I played around with the keybind again, and realized that if I press win key + F4, the ffxiv client registers that as a F4. Of course, when I click the actual F4 key alone, the client doesn't recognize it.

I have used multiple online keyboard checkers, and all of them detect my F4 key correctly.

Every other F keys (like F1, F2, F3, F5, F6...) work as expected. Just F4 is not working.

I'm using steam PC. Any suggestion is appreciated. Thank you!