Hello I am trying to use second display on my Zorin 15.3 but I am not able to find any option to do so. I am using VGA to HDMI to connect with my Asus Rog Strix G Core 8GB.
As you can see there is no option for Second Display or Mirror as mentioned on other troubleshooting forums
I have done this before and also had troubles with it. I am actually using Two Adapters now, both are VGA to Display Port, since doing one to HDMI led to a very similar trouble as yours.
In my case, the trouble was the Nvidia card refusing to recognize two different port inputs.
I needed to make them both use the same type of port. Which was frustratingly annoying...
The adapter or cable is the first thing I would check in this case.
I have checked my cable, its HDMI to VGA cable its working fine on my Windows 11.
What graphics card are you using?
Do you have a dedicated card and an integrated card/
If so, are you plugged into one port on integrated and one port on dedicated?
I am using Nvidia 1650 4gb
I don't know how to check this
Is this a notebook computer or Tower PC?
It's Notebook , Asus Rog Strix G Core
I am not sure, either, then. 
You might preemptively run
sudo ubuntu-drivers install
first, then open Software & Updates, navigate the additional software and check which Nvidia Driver you are using.
Try switching to the 470 (Proprietary) instead. The (Proprietary - Tested) driver is known to have some problems.
