mac mini 2012 late : thunderbolt video problems

I have a MacMini Late 2012. Model MacMini6,1. with the last version of operating system Catalina 10.15.4. I Have been taking the image to the monitor through a MiniDisplayPort to DisplayPort cable, to a DELL 2711U brand monitor without problems. It has been a couple of weeks that the signal is not output on the screen, the monitor says that there is no signal input source. I've tried various cables too, and it only outputs video signal through HDMI. I have tried to make a diagnosis by starting by holding down the D key, but I get the error on the screen "Error 0x800000000000003, Cannot Load 'EFI / Drivers / TestSupport.efi'". I have tried to do with a USB stick, a diagnostic system without success. Someone could help me out. Thank you.