Resolution of monitor using Nvidia graphics driver with Ubuntu 16.04

When I try to mirror an external monitor with my computer, the highest resolution offered in Display Settings is 1024x768. However, both monitors should allow a resolution of 1920x1080. I suspect this is a compatibility issue between the Nvidia graphics driver and Ubuntu 16.04. Other suggestions using “xrandr” have not worked, probably due to the proprietary nature of the graphics driver. Can anyone help?

Please run nvidia-bug-report.sh as root and attach the resulting .gz file to your post. Hovering the mouse over an existing post of yours will reveal a paperclip icon.
https://devtalk.nvidia.com/default/topic/1043347/announcements/attaching-files-to-forum-topics-posts/