So you're just trying to set your refresh rate to 60hz because it is at 30hz right now? If that's the case I would go through the settings built onto the monitor and try changing the refresh rate there. There is no reason for a 1080ti or a 4k monitor to not support 60hz.
Also try this to adjust the refresh rate in windows.
"Adjust the Refresh Rate.
1. Close all open programs.
2. Click Start, and then click Control Panel.
3. In the Control Panel window, click Appearance and Themes, and then click Display.
4. In the Display Properties window, click the Settings tab.
5. Click Advanced, and then click the Monitor tab.
6. Click the Screen refresh rate drop-down menu under Monitor settings.
7. Select the refresh rate you want from the...