Q: Home Sharing

Hi, amoylan.

Thank you for visiting Apple Support Communities.

Below, I have included some basic troubleshooting articles for this issue.

Apple TV: Basic troubleshooting

http://support.apple.com/kb/ht1551

Apple TV (2nd and 3rd generation): Troubleshooting Wi-Fi networks and connections

http://support.apple.com/kb/TS4546

However, this sounds like a possible issue with port blocking, a firewall issue or older password protocol on the router side.  This articles below cover recommended ports for using Home Sharing, the Apple TV and recommended wireless settings.  If you are unable to edit the setting on the Wi-Fi access point, you may need to contact your ISP to make the adjustments and check for router firmware updates.

Apple TV: TCP and UDP ports and protocols used

http://support.apple.com/kb/HT2463

iOS and OS X: Recommended settings for Wi-Fi routers and access points

http://support.apple.com/kb/HT4199

Also, here is an additional resource for troubleshooting issues with the Remote app. 

Remote app for iPhone, iPad, or iPod touch can't connect to iTunes or Apple TV

http://support.apple.com/kb/TS1741

Hope that helps,

Jason H.