The Free-Flow feature on CCS-PRO requires that the host operating system can support an absolute mouse. This is where the mouse tells the host computer where the pointer is on the screen.
Up until the release of a Windows 10 build in Early 2019, it was necessary for you to install our multi-monitor driver to work with more than one monitor. After Early 2019 Windows 10 treated all the screens as one large workspace instead, so depending on your screen layout, the multi-monitor driver was not required. However, after the Windows update on June 8th 2021 "Patch Day", this change has now been reverted, meaning that the mouse pointer will be confined to the first screen unless you install the multi-monitor driver. You will also need to download and use the Free-Flow Configurator to arrange the screen layout.
If you have two host computers, each with two monitors you would need to configure the Free-Flow Configurator layout and upload it to the CCS4-USB/CCS-PRO. The screenshot below assumes that the four monitors are laid out horizontally.