Can't get 4k or even UHD one my monitor when going through a receiver

I've been using an old Acer laptop conntected to a Sony STR 1050 receiver to an HD Plasma TV. The resolution was always set to 1920x1080.
Recently I upgraded to a 4k OLED TV and had some unusual difficulties getting the system to work properly. Initially, the Acer computer stated the optimal resolution for the 4k TV was 800x600. Still, I had it set to 1920x1080. However, when I tried to go higher, the TV screen blanked for several seconds before the computer reverted back to old res. Somewhere in the trial and error of settings, the computer defaulted to a 1920x1080 recommended setting.
I then plugged in my newer HP OMEN laptop and it did allow to set it 4k successfully, even though it stated that the recommended resolution was 1920x1080. So I concluded that my old Acer just wasn't up to the task. But then I plugged it directly into an HDMI port on the 4k TV. Both laptops recommended 4k (38xx x 21xx or whatever it is), so that told me that both laptops are capable of the 4k output.
I then fiddled with the receiver's settings. I noticed there was a 4k upscaling option that was turned off so I set it to 'Auto'. The only difference I discovered was that the Omen laptop now said the recomended resolution for the TV was something like 462x352! I did notice something else but cannot recall when I first observed it: The TV prompted me at one point to allow for "HDMI Depp Color" and the options were 'off' and '4k'. It seems that when the 4k is set to ON, thats when the laptops' recommended resolution is 600x800 and when it is off, it recommends 1920x1080. There is also a 4:4:4 passthrough option on the TV.
I've checked the HDMI cables to make sure they were high speed.
I cannot figure out why the resolution is not recommended to be 4k when running through the receiver and why I cannot set it to 4k with only the one laptop.
Any thoughts?

High speed HDMI cables are barely enough for such resolutions unless properly certified.
Longer lengths need better quality cables, Premium high speed.

Depends on what you mean by older Laptop, mine is from 2014 and cannot do 4K resolutions from the HDMI port.
The Sony STR 1050 receiver is also from around 2014 and may not meet specs for 4K.
HDMI 2.0 specs came in around 2014 as well.

As you are having problems with a newer Laptop as well then the indications are of poor quality and long HDMI cables.

Helmut said:

High speed HDMI cables are barely enough for such resolutions unless properly certified.
Longer lengths need better quality cables, Premium high speed.

Depends on what you mean by older Laptop, mine is from 2014 and cannot do 4K resolutions from the HDMI port.
The Sony STR 1050 receiver is also from around 2014 and may not meet specs for 4K.
HDMI 2.0 specs came in around 2014 as well.

As you are having problems with a newer Laptop as well then the indications are of poor quality and long HDMI cables.

Thanks for taking the time to respond; I've been having some difficulty troubleshooting this nd I would think it is not an uncommon problem.

So, a couple of new observations:
I confirmed all HDMI cables were at least high speed.
I unplugged the master HDMI cable that connects the receiver to the TV - (it's basically the 'monitor output' (with ARC) of the receiver to control what external device's signal is sent to the TV) and plugged it directly into the old laptop. The display settings changed to include UHD, 4k and 8k options and I could select any of them. I selected 4k and the TV resolution instantly jumped to that res. What also happened was the 4k video from YouTube seemed to take several seconds to buffer and would stop frequently for several seconds. This did not surprise me and I assumed it was the old computer not being able to process the info fast enough but thats just a guess. BTW, I selected the resolution on the You Tube video as it had 4k and UHD; the computer was set to 4k. The video was watchable without interruption when I watched it in UHD. This would appear to indicate to me that both the laptop and and cable are adequate to handle these high resolutions. What I found perplexing however was that the display settings stated that the recommended resolution for the TV was now 4k (3,840 × 2,160)! Even stranger was that when I selected the recommended resolution and closed the window, after the display changed, a small window in the task bar appeared stating this is not the recommended resolution. It was a notification from the Intel Graphics Driver and it recommended an even higher resolution (4xxx )

All this alone would lead me to believe that the receiver is the problem but this doesn't explain how when I hook up my OMEN laptop and go through the receiver, the UHD and 4k resolutions are available.

"I confirmed all HDMI cables were at least high speed."

Packaging maybe labelled as such, but are the cables really of the required standard, there is a lot of poor quality cheap cables. The longer the HDMI cables the more likely problems.

As I said your older Laptop and the Sony STR 1050 may not meet newer specs for the HDMI outputs and inputs.

Most people never look at the specs of their older kit and cables, but just buy a higher resolution monitor/TV expecting it to work.