Diagnosis
The monitor is not detecting a valid video signal from the PS5. This is typically a handshake issue related to the HDMI version, resolution, or refresh rate negotiation.
How to Fix It
Power off both the monitor and PS5. Connect them with the included HDMI 2.0 cable. Power the monitor on first. Turn on the PS5. It should detect the display. If the message persists, press the monitor's joystick to open the OSD. Navigate to System > Input Signal and manually select HDMI 1 or HDMI 2.
If That Didn't Work
The PS5 may be outputting a signal the monitor cannot sync to. Boot the PS5 in safe mode: hold the power button until you hear a second beep. Connect a controller via USB. Select option 3, 'Change Video Output'. Set it to 1080p. Reboot and see if you get a signal, then adjust resolution in PS5 settings.
Heads Up
Ensure you are not using the monitor's USB-C port for the PS5. The EX2710Q's USB-C port is for DisplayPort Alt Mode from a PC or laptop only. It does not support HDMI sources.