Whats your wireless protocol on your router? Vizio needs WPA2-PSK, wont work on WEP or WPA-PSK. Get into your router (192.168.1.1 maybe) and change to WPA2-PSK, then try again.
If connected to the router as an access point that would be what it would use, but not as a straight wireless with a passcode.
It got progressively worse over the last year or so and had worked just fine before that started.
Here's one for you.
I bought a brand new Motorola fast *** modem/router recommended by our cable company to take advantage of the highest available speed and throughput only to get it home and find out that it was slow as hell and when I told them what was happening they told me to turn off the WPS function in it because for some reason it interfered with the speed of the modem/router.
It was true, and when I turned WPS off in the modem/router the speeds came up where they should be.
What the hell I ask you, what the hell? :D
I do computer service work for a living and the amount of things that don't work at all or just barely do in our devices these days along with the takeover of commercialism on all of them is pretty annoying.