Sorry if this is a repost but i havent read thru 16 pages.... I've been having constant issues on my girlfriends WiFi network (so has she) but our phones and iPad work at my place - no problem. What worked for us.... Her router was set up using WEP encryption. Mine was WPA2. When I changed her encryption to WPA2... problem solved. Havent had any issues since. I cant remember where I picked up that tip but there's supposedly a bug when trying to connect to a WEP encrypted network.
First off, I had the exact same problem. My Iphone 4 would connect to WIFI everywhere except my home WIFI network. Here is what fixed my problem; and yes I know it seems improbable if not impossible but it is the router that is causing the issue. I called Apple and took notes whille I was onlilne with tech support. Hopefully it will help others that are still having this issue.
1. Unplug your home router
2. Go into your I-phone settings, WIFI, find your network, go all the way to the rioght find the blue circle with arrow in it and tap that.
3.Now hit "forget this network at the top of the page
4. Now go back to Iphone settings--general, all the way to the bottom of the page and hit reset
5. Next hit "RESET NETWORK SETTINGS"
6. Enter your pass code and this will cause your iphone to cycle off and then back on
7. Plug your rotuer back in
8. Once your Iphone has cycled back on goto settings WIFI and find your network
9. Once located tap it and enter your passcode
10. Your I phone WIFI should now be restored.
The way it was explained to me is that sometimes your router just sends invalid IP address out and your Iphone will not except them, thus causing the WIFI will not connect issue. I could not get my IPHONE to connect to my WIFI for almost a week, so that is why I broke down and called tech support. While this may not fix everyones problem, I hope it helps.
I figured out a solution that worked for my iPhone4. I turned off the 3g and cellular data and the wifi kicked right in. Im assuming that the phone is having issue with all the connection options to used. Give it a try and let me know if if it works for anyone else. Go into settings-> General->Network-> Turn off enable 3G and Cellular Data.
For what its worth I had intermittent problems which seemed to start when I first go my Iphone4. About once per day the WiFi link to all devices would drop out and I had to reset the router to re-establish WiFi. I put up with this for quite a while untilI finally contacted the ISP. They finally changed the router to a later "better" version but shortly after they left my home the problem started again; this time much more frequent, every few minutes but it would recover by itself. I finally decided that that the chances of two faulty routers was remote so I reset my Iphone4. PROBLEM FIXED!, How one WiFi device could effect the other devices is beyond me but given the simplicity of the fix its worth a go. I have not gone back to the orginal router to check if it was also ok. Might do it one day out of curiousity.
Have you updated the Router Firmware, as I don't see that mentioned. If the router is older it's quite possible that the iOS version isn't compatible with the current Router Firmware.
I had an old d-link router that worked fine with my iPhone, until recently. Then I started having the wifi connection problem so I bought a brand new D-link with wpa/wpa2 running. I still can not connect to a home network.
back to the drawing board...
I had same problem with wife's iPhone 4 and iPad . . . had to fix both with steps 4-6 in the procedure MadmX posted . . . going to the "General" settings . . . General-->Reset-->Reset Network Settings . . . and then reconnecting to the WiFi network after they rebooted. Both reconnected to the home WiFi network just fine afterward. Did not need to disable the cellular network or cellular data connection on either, or reset the home WiFi routers (4 of them in a meshed WiFi network . . . why is another story for another time).
I had a similar problem.
iPhone 4 would intermittenly connect to my airport extreme wireless network.
And even when my iPhone 4 was connected, the internet connection was extremely slow or non-existent.
My MacBook, Samsung laptop (running Windows 7), and iPad 2 would connect to my aiport extreme wireless network and internet connections were fine on all of these devices.
Enabled wireless guest network --> Problem solved, iPhone 4 connected to my wireless network and speed was fast (12.96 mbps download, 3.96 mbps upload from speedtest.net app).
I don't know why enabling the wireles "guest" network would fix the iPhone 4 connection problem to the airport extreme, but it worked for me and wanted to share it.
Tried many of the proposed solutions kindly provided here but to no avail: kept getting cannot connect when trying to connect to home network but no problem in office network; and then, recall the good old cliche: reboot a/k/a turn it off and turn it on again; so pulled the A/C cable from the Apple Time Cap. and reconnected, and lo and behold, connectivity to the wireless network for the iPhone worked again; interestingly, before the reboot, neither the iPhone nor an older iPad Touch nor even a Kindle wireless would connect to the wireless network; but now, all are back in proper connectivity mode. Hope this helps others.
I've looked at the first & last page solutions and none of them work!
When I first bought my iphone4 it wouldn't connect to my home wifi network. Then I tried Greg's suggestion of clicking 'forget this network' via the blue arrow, and that worked.
We had to re-set our home router last night, and now I can't connect on my iphone4 at all. It is so frustrating. I have wasted nearly the whole day trying to sort this out because I use my iphone all the time.
I cannot believe that Apple can't sort out this issue, considering the iphone is not cheap.
I am disabled so can't get down to re-set the router yet again but I will see if my husband can do so when he gets home from work.
Shame on you Apple!