Vizio Smartcast TV won't stay connected to Wifi.

Might want to call Vizio. It could be an issue with the tv, especially if your other WiFi devices stay connected.

I had the same problem with only one of my Vizio TVs which was my newest Vizio TV. All the other ones worked okay. I searched everywhere on the internet for answer and I finally called Vizio customer support. Vizio customer support had me do the steps below and the TV seems to be working.

1. Turn off the TV.

2. Unplug the TV from the wall.

3. Find the manual ON button. It was on the back right of the TV. There were three vertical buttons and the ON button was the top one.

4. Push and hold the ON button for at least 5 seconds then release.

5. Plug your TV back into the wall.

6. Using the remote, turn on the TV. It took a good minute for the TV to fully turn on.

My TV has been holding internet connection and not dropping offline after the above steps.

That's Vizio's hard reset procedure to correct a lot of different problems due to their poor design ☹️.

So more to add . . . the procedure I described above did not last. My Vizio went right back to continuing to disconnect from the internet. My next step is to run an ethernet cable across my living room to my router to see if that solves the problem. 

Okay. This is my third and last post on the subject. Went through all the troubleshooting with Vizio support and they determined that my TV is broken. I suspect it is a faulty Wi-Fi card. My TV is out of warranty and to have a technician come out sounded expensive to me.  The easy fix was to go buy a $40 Google Chromecast 2, plug it into the HDMI port, and watch all my apps and shows through the Chromecast. (I'm sure a Roku box will do the same.)

So, if you value your time, don't bother with all the troubleshooting. Just go buy the $40 solution and be done with it.

Rather than the $40 solution, why not the $8 solution....buy an Ethernet cable and connect the TV to the gateway?

That's a great solution however not possible for me. The modem/router is in one room of the house and the TV with a problem is hung on the wall and a different room of the house. 

Ack, just realized you jumped onto this thread.  The OP has the TV next to the gateway!

Oh well, at least you have a good option!

What about using a WiFi extender or AP in the room with the tv? You can always just use a long ethernet cable as mentioned above for a test to ensure that it is just the WiFi module that may be broken if the extender doesn't work.

You could plug the TV into the router with an ethernet cord and not mess with the WiFi.

That said, I don't use the built-in apps, the day I ordered my 4k Vizio, I ordered my 4k Apple TV and it's a great experience.  Plus, since my TV isn't connected to the internet, I don't have to worry about Vizio installing firmware updates that cause problems (I've seen lots of complaints on this).