If you are running a screen resolution on your secondary monitor that is less than 1366 x 768, that could possibly be the issue.
If you are running a USB to HDMI adapter for your second monitor that could also be the issue.
Try opening Studio One and go to Studio One>Options>General and disable high-dpi mode.
You can also right-click your desktop and go to display properties if you are on a Windows machine. From there, take a look at your scaling options and make sure you are set to the default of 100 %
If the problem persists, you will want to report it to the developer of the plug-in.