Going into resolution and attempting to create a custom resolution of 3200x1800. I would set the timing to manual and then enter the resolution, but hitting the test button would result in no-signal.

Now, if the NVIDIA custom resolution is not supported by your display, follow the procedures discussed below to set a custom resolution on your Windows computer without any issues.

Under Display, navigate to Change Resolution. Select Customize and then Create Custom Resolution. Set the Horizontal Pixels and Vertical Lines to your desired resolution.