When I go into the display settings there are 2 monitors displayed. When I click on the main laptop monitor, and then slide the display brightness slider, it does darken the laptop monitor. However, when I choose the external monitor (which has different resolution settings) and then slide the brightness slider, it only changes the laptop's display, even though I have the external monitor selected. So no matter which monitor I have selected, the brightness slider only effects the laptop's display. I am running Windows 11 on a Surface Pro 7 Tablet with 16GB of memory. Believe it or not, but one time I booted the tablet and the external monitor was at full brightness, but then the next time I rebooted it's back to being dark.

Your suggestion about installing the Win10 driver, can you explain what I need to do? I download the driver and then how do I get into compatibility mode?

Thanks for your help with this.

Thank you, it said it was successfully installed after right clicking on the .inf file and choosing install. Now what do I do? The monitor has not changed, it's still dark. Going into the display settings the brightness controls still only effect the main laptop monitor no matter if I choose monitor 1 or 2.

I have rebooted many times. I did adjust the monitor's own on-screen display to 100%, that was the first thing I tried. I have plugged in the display and reseated the cable several times. Attached are screen shots of the device manager and also screen display.

There is no change with the external monitor brightness depending on room brightness. One suggestion I saw was to turn off automatic brightness control, but on my version of Win11 that option doesn't even appear. There is a "Night Light" option to use warmer colors, when I select the external monitor and slide the bar, both displays change. If I select the internal monitor and slide the "Night Light" option, both displays change.

However, when I slide the "Brightness" bar, only the laptop monitor changes, even when I have selected the external monitor.

Two times the external monitor has been at normal brightness, but reverts to being dark on reboot.

I have tried to change the external monitor to "Make this my main display" but the adjustments appear to effect the screens the same.

I think this is a Win11 problem as twice the external monitor has been at full brightness, but the System/Display options don't effect both monitors the way they should, using the brightness option only effects the main tablet display, even when the external monitor is chosen.

I am traveling and the hotel's TV only has an HDMI input jack, not an output, I then tried it on my partner's Mac but I don't think the mac supports dual monitors, I then plugged it back into my tablet and it's now at full brightness (see attached photos, one with dimness and one at full brightness). I have a feeling when I reboot it will be dark again, but I think this is clearly a Win11 problem and not a problem with the Acer monitor. I thank you for your help resolving this issue, I'm just sorry I wasted your time on a problem that was not Acer's fault.