Did you transfer the backup for your iPhone 3 to your iPhone 4S?
If so, try resetting network settings on your iPhone 4S at Settings > General > Reset > Reset Network Settings. This will erase all saved wi-fi network settings from the iPhone.
If not, try resetting your wireless router. Power off or disconnect the wireless router from the electrical outlet followed by powering off or disconnecting your modem from the electrical outlet. Wait 5 minutes followed by powering your modem back on allowing the modem to completely reset followed by powering your wireless router back on allowing it to completely reset with your modem and try again.
Test under a different Wi-fi network if possible.
Make sure your software is up to date ( Settings > General > Software Update)
Place the device in to Airplane Mode ( Settings > Airplane Mode "ON") and then Turn OFF.
Test wifi again
Make sure your entering Password correctly x 2
Reset Network settings (Settings > General > Reset > Reset Network Settings
Attempt to join again
If no success go back to (Settings > WiFi > Forget this Network)
Does "did a reset at home of the modem and all" include this copied from my previous post?
Try resetting network settings on your iPhone 4S at Settings > General > Reset > Reset Network Settings. This will erase all saved wi-fi network settings from the iPhone.
tried all you said. Nothing. Tried to do your last step but I don't see the when going to settings>WiFi> (Forget this Network). When I go to Settings> WiFi> says not connected > to choose network, no option for Forget this network.
Yes that was all from your previous post. When I tried what you said about going to Settings>General>Reset Network Settings, it still pops up with the original setting for the home wireless. Its not deleting it.
After resetting network settings at Settings > General > Reset, it still pops up with the original setting for the home wireless where?
Resetting network settings does not prevent an available wi-fi network your iPhone is in range of from appearing when going to Settings > Wi-Fi.
Resetting network settings erases all saved network settings for all wi-fi networks your iPhone has successfully connected with previously.