Cannot reach particular website when connected to AT&T Wi-Fi

That's what I suspected.  You're probably not going to like this, or maybe even believe this, but...  I think the problem is not AT&T; it's the website or its network security.  It may be triggered by your AT&T-issued IP address, but that's not AT&T's fault.  Or your fault.  AT&T is getting the traffic to GTT.NET / NODEFOUR.NET just fine, even though the server seems to be in the UK somewhere.

It looks like to me that you're not getting a response because, somewhere in that network, it was decided not to respond to your traffic.  Maybe your IP was previously used by, or is in the same IP block with, someone who got on a bad-actor list.  You've eliminated some other possible reasons why your traffic would be dropped by successfully using the same device on a different network.  

Let's help you get access to that website, @japortela!

Try the following troubleshooting options from our article that covers the topic of websites not working:

• Delete cache and cookies - Think of this as housekeeping for the browser. 
• Flush DNS - This may improve how web pages load. 
• Disable IPv6 - This could help improve browser load times.

We also recommend restarting your gateway to refresh your Internet connection. This can be done manually by following these steps: 

1. Unplug the power cord from the back of your gateway or modem. If you have: 
   • An internal battery backup, remove it
   • DSL, unplug the phone cord from your modem or gateway
2. Wait 20 seconds.
3. Put the internal battery back in if you have one. 
4. Plug the power cord back in. If you have DSL service, reconnect the phone cord.
5. Wait for the gateway or modem to restart and your Broadband light to turn solid green. This can take up to 10 minutes.

Let us know how it goes!

Lacey, AT&T Community Specialist 

Or, you can disable AT&T Internet Security (or Active Armor or whatever other name they're calling it) and be back in business.  From the tons of reports we get in this forum, the primary "feature" of this software is to block legit sites and not give you a way to whitelist them because they don't throw a notification.

@tonydi yeah, that stuff is all turned TOTALLY off. Agree 100%

@ATTHelp Thank you for taking the time to forward that. None of this stuff helps. I can bring any random device off the street, bring it into my house, connect it to this Wi-Fi, and the site doesn't work. I've done every single logical elimination step imaginable. The problem is DEFINITELY upstream from my devices. Not only did I "restart" the gateway, I completely reset it to out-of-the-box state and no effect. Not to sound like a know-it-all, but I'm a qualified network engineer and not a typical layman customer. Just giving context here.

What error or message do you get from the browser when you try to visit one of these sites?

What results do you have from TRACEROUTE both from the AT&T Wi-Fi and from your mobile carrier (or somewhere else)/

@JefferMC Good evening!

1. "This site can't be reached... <URL> took too long to respond"

2. screenshot follows

3. screenshot follows

Looks like with traceroute both networks make it to devices on this 77.111 network the same before both started returning stars back to me.

@JefferMC that is actually super interesting. Also explains why it worked just fine until last week, communication was super glitchy, then just quit altogether. I’m not bad acting, just trying to file reports LOL (I know what you meant, was just makin the jokes)

@JefferMC i will happily entertain any logical explanation. thanks again.

Thanks for getting back to us and providing additional information, japortela.

A good way to access the website on your network is by using a VPN. We also recommend contacting the site host to make sure there's nothing happening on their end that could be causing this, especially since that's the only website you can't access. Based on the traceroute, we're inclined to believe that the problem is not on AT&T's end.

If you need assistance with anything else, just let us know.

Thank you for visiting the AT&T Community Forums.

Aminah, AT&T Community Specialist