Windows 10: When I connect my PC to my Monitor, the Monitor shows No Signal and turns into Power Saving...

When I connect my PC to my Monitor, it shows "No Signal," switches to Power Saving Mode, and then turns off. This is a recent problem which has emerged after 5 years of flawlessly using my PC. The PC is not the problem and neither is the cable, as I'm typing this while being connected to my TV. I'm thinking I might have to change some settings in the Monitor. How do I do this, without the monitor turning off on me after 5 seconds?

:)

 

Monitor Power Saving Mode

I can't disable anything due to as soon as I turn on the PC the monitor shows the text 'entering power save mode' meaning I am unable to use it at all.

I have tried doing the things listed but have found it made no difference

 

After power outage PC turns on, but there is 'no signal' on the monitor.

After a power blackout, I powered up my PC. It turned on but there was 'no signal' on the monitor. Then it just goes to sleep. My lap top and iPhone work fine. Unplugging and plugging didn't work. Besides getting a new computer or taking PC to hardware
tech, is there any other home remedy?

 

Monitor No Signal Issue

Computer is an optiplex 7080 used for work. Monitor is LG with the only applicable port being hdmi, as the PC only has displayport available for the monitor. Connected via an adaptor from displayport to hdmi. Computer and monitor have worked fine together in the past, however after a forced restart the display only gets as far as DELL before going black with a "no signal, switching to power saving mode" message. On boot the monitor occasionally displays a message that the resolution is incorrect. Both doing nothing and attempting to adjust the resolution do nothing. No menu option aside from input is available from the point of no signal, and attempting to change the input from the monitor yields a pause and then "no signal, switching to power saving mode". Can access monitor menu for about 2 seconds while DELL is displayed, but then promptly shuts down with yet another "no signal, switching to power saving mode". Have tried many different combinations of unplugging, replugging, powering down, power cycling the computer and monitor, and yet nothing changes excepting less responsiveness.