It was our very old XP machine. We factory restored it and it won't connect. Turns out that we needed to update the WiFi driver after the OS was updated. Confirmed.
I have a Dell Latitute E5530 laptop that won't connect to my secured home SSID. I have 2 other laptops connected to it wireless, plus phones, plus 2 TV's (via a Roku and a Chromecast). I thought there might be a limit to what I can connect (i.e., 5 devices), however I brought home a 2nd laptop from work and that connected with no issue while the Dell Latitude still cannot. I don't even get the option to type in the Password Key, it simply says "Cannot connect to the network". I'm able to connect to an unsecured network with this same machine, no problem. I've tried reset the network adapter, I'm just stumped at this as to why this computer won't connect.

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