Question i suddenly lost 2560x1440 resolution and playback speakers on an hdmi monitor

May 25, 2022
I dont know how or why this happened.
For over a year the setup I have worked normally, meaning the 27" monitor had the 2560x1440 resolution to select in the list of resolutions in display settings, and its built in speakers showed up as a playback device in the sound applet.
Literally, it was working this way yesterday.
Then, today, i turned the pc on, and the 2560x1440 option was no longer in the display/resolution list, and the monitor's speakers were no longer in the playback devices list, and i cannot get them back!
The only thing I can think of that may have changed anything is windows updates, but I may be wrong about that.
E.g. I was watching the cpu usage spike, and the windows update service was using the most of the cpu, but then the cpu usage went back to normal, so i did not think there was anything wrong happening....until i realized the resolution and sound settings had disappeared.
I cold booted and reseated all the cables, but that did not fix it.
I checked the device manager, and it showed "PnP monitor" for the 27" monitor (i never checked this before so i dont know if that was different before, i did not check becuase the first time i plugged the monitor in a year ago, the 2560x1440 resolution was right there).
So, I went to the dell website and downloaded and installed specific drivers for the monitor, and now the monitor says this in the device manager, "dell 2721d hdmi1".
That is nice because that matches what the monitor actually is, but i still do not have the resolution or sound options.
Also, when the pc powers up, the monitor itself says "no hdmi signal from your device", but then when windows finishes starting the monitor works normally (although at the lower resolutions).
I apologize, i am not sure if it has always said this, again, it worked normally when i first set it up, so i did not take note of that.
For video ports, the pc has display ports, and i am using display port to dvi adapter, and a cable that has dvi on one end and hdmi on the other end, and it is plugged into the monitor's hdmi 1 port.
I know that's a lot of changes, but like i said it has worked normally until today.
Also, I have an hdmi cable with hdmi on both ends, and an hdmi to display port adapter, and i tried this, and it did not fix it either (...making me think it is not the cables causing the problem).
This may be important, but i just dont know (im at my wits end).
When I first plugged the monitor in a year ago, the volume on its speakers was normal.
Then suddenly one day (again without changing anything), the max volume was barely audible.
I never figured out why that was happening, and I just used other speakers.
Then one day the speakers got louder again, and i had not changed anything.
This is bad for me, because the higher resolution means everything to me to fit more on that screen.
I'm stumped as far as what to check next.
Can anyone help?
thank you,
May 25, 2022
more detail:

I dont know if this matters, but when i noticed these problems, i had a usb webcam plugged in, and in the sound applet i disabled the mic on the webcam and made the mic jack on the front of the pc the only device that was enabled.
I did this so the windows camera program would use just the camera part of the webcam, and it would get sound from the mic jack on the front of the pc.
I did not check if the missing resolution and sound options were already gone when i was doing this, because it had been working normally forever, so i did not stop to notice anything about that.
I want to suspect something simple like the cables and adapters, but like i said, the 2560x1440 resolution was right there to use the first time i plugged the 27" monitor in.
Also, i looked at the hdmi cable and hdmi to dp adapters, and they both say 4Kx2K on them.

This is the last twist, when i was enabling just the mic jack on the front of the pc, I was also connecting a third monitor.
The pc has a vga port, which is connected to a 19" monitor, and 2 dp ports.
one dp port is connected to the 27" monitor, and the other is connected to an HDMI a/b switch so I can share a third monitor with another pc.
I was flicking the switch on the ab switch and i was not getting any picture to the 3rd monitor, so i unplugged then re-plugged the dp parts of the video cables that plug in to the pc itself, and ultimately all 3 monitors worked.
But...that is when i noticed (again i cant say that is when it actually changed/happened) the 2 problems.
note, i have been using this 2 and sometimes 3 monitors thing since the 1st time i plugged the 27" monitor in, and it has worked normally, so i cant see how that could have caused this problem...unless doing both things at the same time somehow "overwhelmed" windows (i would hope such a thing is not possible...)

I feel so inadequate...i thought i was good at figuring these things out?!
can anyone help?
thank you again