Look at iOS Troubleshooting Wi-Fi networks and connections http://support.apple.com/kb/TS1398
iPad: Issues connecting to Wi-Fi networks http://support.apple.com/kb/ts3304
iOS: Recommended settings for Wi-Fi routers and access points http://support.apple.com/kb/HT4199
Additional things to try.
Try this first. Turn Off your iPad. Then turn Off (disconnect power cord for 30 seconds or longer) the wireless router & then back On. Now boot your iPad. Hopefully it will see the WiFi.
Go to Settings>Wi-Fi and turn Off. Then while at Settings>Wi-Fi, turn back On and chose a Network.
Change the channel on your wireless router (Auto or Channel 6 is best). Instructions at http://macintoshhowto.com/advanced/how-to-get-a-good-range-on-your-wireless-netw ork.html
Another thing to try - Go into your router security settings and change from WEP to WPA with AES.
How to Quickly Fix iPad 3 Wi-Fi Reception Problems
If none of the above suggestions work, look at this link.
iPad Wi-Fi Problems: Comprehensive List of Fixes
Fix iPad Wifi Connection and Signal Issues http://www.youtube.com/watch?v=uwWtIG5jUxE
Fix Slow WiFi Issue https://discussions.apple.com/thread/2398063?start=60&tstart=0
Unable to Connect After iOS Update - saw this solution on another post.
Note - When troubleshooting wifi connection problems, don't hold your iPad by hand. There have been a few reports that holding the iPad by hand, seems to attenuate the wifi signal.
If any of the above solutions work, please post back what solved your problem. It will help others with the same problem.
Ya, I was still able to run PC, ps3, and smart tv as well. But after the update, no idevices worked. My routers bandwidth was not high enough. The update requires you to have at least 5ghz for the iPhone and iPad to work. It was baffling to me because it worked fine before the os6 update. Like I said, I went many frustrating days renewing leases and tinkering with my old router, changing security options, everything I could try but my old router just wasn't cutting it( an older NETGEAR model) your router could be new but still not pick up the bandwidth. I bought a Cisco linksys e2500 with dual bandwidth capabilities 2.4 + 5ghz, and then I was back online just like that. You need at the least the 5 ghz bandwidth. Like I said, if all else fails for you, I would try it and I'm pretty sure it will work for you, plus the performance and overall signal is significantly stronger
Really? No backward compatibility? I'm having this issue at our school with six new iPads I just bought. Our network has b/g/n, but no 5 GHz. We're in the process of getting quotes to redo our wireless infrastructure, but until that is accomplished we are out of luck? Wow, I'm in dissappointed in Apple.