Q: iphone 4 cannot find wifi

Did it ever see and/or connect to that network before? Do you have MAC filtering on for the router? What settings do you have on for the router? What security do you have on for the router and your Wi-Fi network?

You may need to double-check the router settings. It may be that it is only showing the 5GHz Wi-Fi network and that could be why the iPhone 4 is not seeing it. Try logging into the router and checking the Wi-Fi network settings. I'm not sure if you tried a reboot of the router, powering it off for 30 seconds or more and then powering it back up again.

Linksys routers are usually pretty easy to set up, however if you reset it, you may have to set it back up again. Also, if the network is still showing up on the phone, click on forget this network, and then go back to reset all settings on the phone and turn on wi-fi again and see if it "sees" the network.

@dchmielowski

First thing I want ask you, have you view the link below to troubleshoot your current issue:

If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network - Apple Support

If yes and it was unsuccessful then I would reach out to Linksys and check the router firmware.  Chances are it maybe be running an outdated firmware.  Please call the numbers below to move forward.

1. Customer service: 1 (800) 546-5797

2. Technical support: 1 (800) 326-7114