Chosen Solution
I have a HP 2159m display and it won’t longer display any video, It won’t show on device manager but it seems that it know that it’s being plugged in. Display: HP 2159m PC: Asus Gaming TUF FX505DT
Typically, being plugged in is determined by a wire in the cable being grounded when plugged into a monitor. In order to show in the DM, the computer queries the device. If it does not get a response it has no idea what it is. Best to plug the computer into another monitor as an HDMI or DV circuit is not the same as a DVI or VGA port circuit. Some monitors have multiple ports. If yours does you can try a different connection.
Can you open the monitor and check for any leaky or bulged capacitors? I have attached a picture below for reference.
