I've had something similar happen to me twice this summer, and thought I would share a possible solution for the problem.
I have an Airport Extreme with two networks: A closed home network, and a guest network for guests with guest network priviledges. For whatever reason, my iOS devices will sometimes switch to the guest network, which does not allow for Remote use. I'll troubleshoot the heck out of not being able to see my iTunes library until I eventually stumble onto the fact that I am on the wrong network. Make sure you check that your wireless connection is on the network associated with the iTunes/Home Sharing setup as a part of your troubleshooting.
I have itunes, apple tv, and remote app installed on my iphone and ipad. The remote app, does not matter whether I use it from the iphone or ipad, is not working... Although, I can still stream media from itunes to apple tv, meaning there is actually no problem with the network setup. I suspect there is a problem with the remote app.
Called Apple support for the issue, the guy asked me to make sure Apple TV's required ports are open on my wireless modem. The ports are explained in the below link.
I haven't been able to contact my internet provider for help yet.
It might be helpful for you.
Keep us posted
Mar 2, 2014 4:38 AM
I did a geeky thing: The problem is NOT with your Windows Firewall. The problem is with the firewall settings on your router (wireless router settings that you have to sign into as administrator online). *WARNING: If you are scared to mess with settings, let someone else do it for you.
Step 1: Log on to your router from the provider's online page (for example Sky or BT router settings)
Step 2: Look for a button that lets you set up wireless access to your devices. (For example, in Sky, it's called "Wireless Station Access List" and has a blue button next to it called "Setup Access List".
Step 3: Click that button and you will see a list of wireless devices that are detected, for example iPhone, iPad etc. *NOTE: You can only allow one at a time, so you have to select one and let it be accepted, then go back and do any others individually.
Step 4: Click "Apply" or "Save" or whatever your router tells you to do and you're done!
When you go to your device, it will ask if you want to trust that computer (meaning your own PC)..say yes. By magic, the "Remote" app will show your iTunes library and you're ready to roll!
I am not good at IT but it took me months to find a solution by trial and error and now it works! Yaaay!
FeezafeeiPhone 4, iPad