If the resolution changes while Fences is not running, it will not auto adjust the layout to the new resolution. This feature seems only work in changing resolution while Fences is running.
For example: Turn off the computer, plug in a monitor with another resolution, boot the computer. Fences will not adapt the layout to the new monitor.
This usually happens like, in my office I have a 2K display, after work I turn off the laptop and go home, then if I boot the laptop with its built-in 1080p display, Fences will not auto adjust the layout.