As I wrote, I have a same device, and the app is working fine through WiFi. Can you browse the web via WiFi? Check your connection, and if you can visit some webpage, but the app isn't working, then try to reinstall the app. Check your router! Can you connect you iPod with your PC via WiFi? If you have problems yet, try to contact with the developers!
Papelbon: you're right, these are 3 gen of iPod Touch. The last gen (3rd) showed up with 32/64 GB storage capacity (more RAM and powerer processor), the 8 GB 3rd gen iPod Touch has same hardware than the 2nd gen iPod Touch. The 4th gen iPod Touch will be showed up soon (early fall).