External Monitor Issue

PC Make/model: Asus Vivobook Pro X580VD
External Monitor(s): Lenovo ThinkVision L2251x Wide (displayport) and then some random LG (HDMI)

Issue: I have never had issues using external monitors for the past 2 years with this laptop, always worked perfectly fine up until a few days ago. I attempted to use a DisplayPort for the first time (I didnt know it worked unidirectional and that the output has to be DisplayPort i.e. the computer) so I plugged the HDMI in my laptop and the DisplayPort into the Lenovo monitor and it didnt work. I tried many things to try and resolve so I gave up (and then I realized my issue, the DisplayPort on my PC is through USB C).
The REAL issue I have here is since I gave up, I decided to revert back to a regular HDMI-HDMI interface with the old monitor that worked usually fine. All of a sudden it did not work anymore, I am not sure if my attempt with the DisplayPort (DisplayPort - HDMI) ruined my HDMI port on my laptop? I tried everything from restarting my laptop and unplugging the cables, unplugging the monitor to power reset, try rollback the graphics driver, setting BIOS on default settings, literally everything and nothing seems to work.

When I plug it in, the monitor lights up and can clearly sense it and it says "No Signal, entering the power save mode shortly". Then when I unplug it, it says "No Signal, please check your connection"

 

I had that happen to me once...the HDMI port on my laptop stopped working...and it turned out that it was grounding issue with the LCD-display. But that was with a new LCD, while you are working with an old one. Just for kicks, can you try a different display with HDMI?