This article discusses every potential solution for Ready or Not not working on PS5, as well as the most probable reasons why it's occurring.

A new PS5 system software beta has added the ability to pair a DualSense controller with multiple devices at the same time.

This includes use on two separate PS5 consoles – such as a standard model and the PS5 Pro. You can hot swap the DualSense between them by pressing the dedicated button.