This article outlines the functionality and caveats of UPS sync control.
The UPS Sync Control option allows you to have two or more UPS units with their output synced up with one another. In this scenario, you can remotely turn off or reboot one UPS and it will turn off/reboot other UPS units in the same sync group. This option is primarily used in cases where you have either a server or switch that has redundant power supplies. You will need one UPS per power supply. If one UPS were to become unavailable, then the other UPS will support the other power supply. Lastly, bypass is NOT a supported control option.
However, if the you need to reboot the server/switch, you need to ensure that all power supplies are being rebooted. In this case, the sync group allows the user to reboot one UPS, which in turn, reboots all that are part of the sync group. A problem that could occur is that if you had two UPS units that are part of the same sync group and are the two UPS' being monitored through PowerChute Network Shutdown. If you were to turn off/reboot one of the UPS units, the other would turn off/reboot as well. When this happens, the server would turn off/reboot as well.
This is why we don't advise enabling sync control when using PowerChute Network Shutdown without making sure you configure it for a multiple UPS scenario/configuration.