Vizio Tv Connection Issues with Home Internet

I had the same issue and got it to work by resetting my Vizio to original factory settings. Once it prompts for Wi-fi, the T-Mobile box takes right away

How to connect WIFI (vizio.com)

I have a 3 year old Vizio and was able to connect to the 5G network no problem. Initially, though, I forgot both my DirecTV streaming box and my Roku stick both need their own separate connection to the network. Once I took care of that everything worked fine. I did have to create a separate 2.4G network on the gateway to use for my HP printer and my air conditioner before I could get them connected, but that solution worked perfectly on the first try as well. A couple of things I'll mention, though you may already be aware - make sure you are using the WiFi network password, not the provided admin password printed on the gateway device. Secondly, make sure you go to advanced settings in network management and for each network manually select 5G or 2.4G. The auto detection feature does not seem to work very well. 
One last thought. We recently had a brief power outage in our area. When everything came back up, I had to do a reset on the gateway before anything would connect again, so that's another possible tactic to try. Hope you get sorted out. 

I'm planning to call T-mobile and approach this situation this week as soon as I have time.  I've been dealing with this same issue for two months. Vizio TVs continually disconnect from the Internet. It is not the Vizio TVs ;obviously! ..that is just laughable. Rarely they will reconnect after continuously trying. Their mesh units are already infamous for problems across the US. I have had nothing but issues since I've gotten T-Mobile Internet. They told me I had 5G deep red status in my area as well, but clearly do not. I wanted T-mobile to work so bad that I bought a $400 antenna to boost the signal of my router. I have yet to install that, but I am weary that that will have any impact on the Vizio TV connection issues. Logically it shouldn't. If T-mobile doesn't own up to their problems and give back (in a meaningful way) for almost 3 months of repeated technical issues & time spent trying to resolve with their team and their third-party team, I'm going to have to go with someone else. Id just have to give up on them. It's sad because I have been a loyal advocate for T-mobile for a number of years now. They have risen through the ranks to almost Verizon status. They would've been there if they got the Internet right from the jump. Clearly, they are having major issues with it and that's fine for anything new but if you're not gonna own up to it and you're not gonna give back to the customers in a meaningful way , you just dropped status back down to all of these random garbage companies. Have integrity and I will stay. We shall see. 

I saw this and it seems like the same problem I'm having. My phone is connected but my Samsung smart TV keeps saying "wireless network connection failed" and just will not connect. 

So what do I do guys???? Buy another router and connect it to the TMobiles gateway router? 

I tried the 2.4 with the above suggestions and it still didn't work. What I did was use my old router connected to the new router through a network cable and it works. Not ideal but it's a work around until I figure out what the fix is. I contacted customer support at T-Mobile and they pointed their finger at Vizio and said it's the TV's problem not T-Mobiles router. I wasn't impressed with their customer service. 

Dude the internet wouldn't even work for me. I had them send two different routers none worked right, my phones were legit faster than the home Internet and they said 5G in my area was fine but it obviously wasn't. I currently have spectrum which is way more expensive but better, was thinking about switching to frontier, hear good speeds from them

On the 2.4GHz network, change the WPA security to WPA/WPA2.