There are different connection issues reported on this thread, from office setups to 3g not working. Without additional diagnostic steps it would be difficult to resolve. My general recommendations for Wi-Fi issues (not cellular) are:
1) Upgrade to iOS 9. The Networking Routine was changed in iOS 9.
2) Perform a Forced Restart: Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. Allow device to restart.
3) Reset Network Settings: Settings > General > Reset > Reset Network Settings. Rejoin the Network again.
4) Change to Google's DNS: Settings > Wi-Fi > Click on the Network, Delete all numbers under DNS and enter 126.96.36.199 or alternatively 188.8.131.52
5) Reboot Router/Modem: Unplug from power for 2 minutes and plug again. Update Router Firmware (check manufacturer’s support website). Verify your router is Wi-Fi certified.
6) Determine if other Wi-Fi devices on network are working well (other iOS devices, Macs, PCs).
7) Try device at another Network, i.e., neighbors’, public coffee house, etc.
8) Restore the Device (ask for additional for details if desired).
9) Go to an Apple Store for hardware evaluation.
I updated two devices to iOS 9 yesterday - was having issues with iOS 8 but no longer with iOS 9. Good luck...