If you're not seeing content that you uploaded there are a few things to check:

a) Did you apply the content to the correct playlist (the one that is assigned to your player)?
b) What duration time did you assign to the content - did you set it to invisible by accident?
c) Click on the relevant playlist and then Schedule. Is this content scheduled to play on the correct days/times?
d) Have you rebooted your player(s) and ensured that they are connected to the Internet?

One final thing to check is to click on your player in XOGO Manager and then select Realtime mode. If you can see your new content in Realtime mode, that means it was successfully downloaded by your player. If the content is on the hard drive but not playing, that means it was very likely set to invisible, or is not scheduled to play on the correct day/time.