Try adding it via nvidia panel.

Reflex has to be implemented in the game. Control panel has no option for it. In case you mistook it to mean ultra low latency mode, it's not that. Reflex is something different.

The Nvidia Reflex option gets greyed out, I can't turn it on. The input lag is pretty bad in this game without Reflex. It's jarring to get more FPS and have the game feel much worse.

Reflex is forced on and can not be disabled with DLSS3 as far as i know so it's probably the same with FSR3 but dunno if it really works you can use SpecialK to test it or even force it if nothing else works.