Welcome to the Apple Community.
Assuming this is not the first time you have used your Apple TV
- You might try restarting the Apple TV by removing ALL the cables for 30 seconds.
- Also try restarting the router.
- If the problem persists, try a restore, you may want to try the previous procedures several times before doing this.
If this is a new Apple TV, it may also be that your network router is not allowing access to the timeserver, check that your router allows access over port 123.
Actually this is the first time using my/any apple tv. The wife and I rented a movie on iTunes last night and I was going to play through the HDMI port on my laptop but had difficulties......cue up the apple tv still sitting in the box. I figured it would be a very quick setup and we'd be watching our rental in no time. I'll have to dig into my cable modem/router settings and figure out what's going on. I'm assuming that will likely be the problem at hand. Thanks for the heads up on the port 123. I will certainly look for that.