My HDMI connection to my second monitor no longer works

alphanumeric said:

Press the Windows Log key + P, then press the up arrow key and enter. You may have to do this more than once. Eventually it will switch you back to PC Screen only and everything will launch on your laptop screen. There is probably a special function key that does the same thing Fn plus an F key with a picture of a display on or above it.

Why your monitor won't work is another issue. I'd swap the cable out as the first test.

I just hooked up my monitor to an older laptop which runs Windows 7. The display came right up with no trouble. So the problem has to be on my Windows 10 laptop somewhere.

EDIT: And now it's working fine. lol I wonder if it was just a loose connection.

If I don't experience any more problems within the next couple of days, I'll mark this as "solved."

The problem has returned--sort of. Here is the sequence of steps I followed:

1. No display on my second monitor, despite the fact that the HDMI cable was connecting my computer to the monitor.

2. Tried changing the -P settings repeatedly. Nothing. When I set the connection to "extend," my computer clearly thinks that there is a second monitor (all the Windows icons go there--as I have it set to my #1 display), but it is completely dark.

3. Tried multiple restarts. Nothing.

4. Tried connecting it to my older laptop as described above. Worked perfectly.

5. Plugged it back into my current laptop. Works just fine now.

So clearly it's some sort of software or setting issue. Can anyone tell me how to fix this if it comes up again without having to resort to using my old laptop, in case I don't have it around?