Where does that code run? Update or FixedUpdate? The "Down methods must be used in Update.
Some keyboards don’t support various key combinations, although Shift+anything seems like it should be supported. Does that combination work in other software on your computer? Test that to eliminate a hardware issue.
It’s used in the Update() function.
“delete” only works - and all other combinations with “shift” + “key”. (i have tested some other keys… Home and End work well)
“shift” + “delete” in combination not.
It seems likely that it’s a combination the keyboard hardware doesn’t support then. I suppose it might be something in Unity as well but I would be surprised by that.
Try loading up a game that allows key remapping and see if that combination is allowed.
It’s also worth checking if it works in an actual build of the game, the unity editor sometimes consumes certain keypresses if you are running within the editor (ctrl based copy/paste combinations come to mind)