We'll need some specifics in order to help you troubleshoot, but let's start with the following:
Are you using XOGO Mini players or are you using your own Windows/Android/Chrome/Fire TV devices? If you have XOGO Minis, they are designed to run 24/7 as long as they are plugged in.
Can you tell us what you are seeing on the TV screens that your players are plugged into? Is there an error code, a XOGO logo, or are the screens just black?
Have you checked that all of the cables (power and HDMI) are plugged in and that your TVs are set to the correct HDMI input?
Some players including the original XOGO Mini are designed to run 1080HD content but will not display super-high-resolution content like 4k. Do you have any content in your playlist that is more than 1920 x 1080 in resolution?
Please let us know about the items above and we'll continue to help you troubleshoot.