@akinyicky  Assuming you've made sure to select the correct input in all of your tests, what exact cable setups have you tried?  Not all cables that you can physically plug into a connector on each end will give you a working setup.  For example, a DisplayPort to HDMI cable can only be used to connect a DisplayPort output on a source to an HDMI input on a display.  It cannot be used to connect an HDMI output to a DisplayPort input.

Thanks for your response. It is good to know that my DisplayPort to HDMI will only work when DisplayPort is the output. I have tried using a laptop that is docked with two HDMI outputs. The monitor still won't recognize an HDMI output though.

@akinyicky  In that case if you've already verified that the same system and cable work with another P2219H, and you've made absolutely sure that the problematic P2219H is set to its HDMI input, then there may be an issue with the HDMI input of that display.  One possible workaround if the system you're using has a USB-C output that supports video output -- which is an optional feature of USB-C ports and therefore not always implemented -- would be a USB-C to DisplayPort cable.  If the problem only affects the HDMI input on this one display, then that type of cable might allow you to keep using that display through its DisplayPort input.

@akinyicky  D’oh! In that case my last resort suggestion if you can access the display’s built-in menu would be to perform a factory reset, but I’m not sure that’s even possible when there’s no active signal being displayed. Other than that, based on everything you’ve tried thus far, I don’t have any other suggestions at the moment.

Thank you for the suggestion! Currently, it is not accepting a USBC to Display Port input either.