Make sure you're holding down the right thumb stick, then press & hold (for a second or so) down on the d-pad.
Having the same issue on PS4. Since new core update I can’t take screenshots using the square button. Is this a known bug?
It all seems to work for me. A bit more awkward though and you have to be careful not to move the reverser instead.
I can take them with R3 and Down, but they always fail to upload since switching to PS5 version. Assuming there's still plenty to fix on DTL!