5g home internet - some sites won't load

I'm sorry, I'm not on VPN. I am apparently a difficult case! 

You can see why I didn’t want to get on the phone for this ;-) 

Are you running over a VPN by chance?

Fails to load on Mac: Chrome; Mac: Firefox; iOS: Chrome; iOS: Safari; Android: Chrome. 

So 3 browsers on 3 operating systems all behave (fail to load judiglova.com) the same. 

Are you using Chrome on your Mac?

Thanks! I tried this on your advice. For anyone else reading this, let me save you some time. You can't disable IPv6 from the System Preferences control panel. You can only set it to local. So I did that, but I also googled and found this Terminal command to disable it: 

networksetup -setv6off Wi-Fi

And that does indeed show as “off” in the IPv6 panel of System Preferences, once you execute it. 

So thus set up, I tried again, and… no change.  :-/  

Some further data though: The site loads on my iPhone via Verizon cellular data, but NOT when the iPhone is attached via wifi to the Tmo 5g Home router. So does that point to the router, not the computer? 

I am able to load that site up without a problem.  Someone else on one of my threads mentioned having an issue with a Mac and it may have been related to IP6.  I'm pretty sure my router is only doing IP4 but when I connected to the modem directly it was doing IP6.  Are you able to force yourself to IP4 and see if that helps?

Thanks! I had been using Cloudflare's servers. In testing, I reverted to the Tmo ones, and neither set worked. So I just tried your google ones, plus rebooting and renewing the DHCP lease, but no change. 

The error messages I see on the sites that won’t load are either “timed out” after a long pause, or 

"A network change was detected. ERR_NETWORK_CHANGED" 

I don't think Tmo is blocking anything on purpose, since these are inoffensive sites. But they won't load. Here is one example site that won't load for me via Tmo. http://judiglova.com/

I have never run across a scenario where T-Mobile is blocking access to a site.  However, since I'm using a dedicated wi-fi router that's providing DNS for my network as well.  You could try hardcoding your DNS servers on your clients to see if that helps.  Google's servers are free to use: 8.8.8.8 and 8.8.4.4.  This would help confirm / eliminate a DNS issue.

Thanks Jlillard, but the device is consistent with the sites it refuses to load, so it’s not an intermittent or random occurrence, and I do not think it’s a heat-related issue in this case. 

I’d like to continue to solicit advice on this. 

If you have one, I would suggest a dedicated wi-fi router that is hard-wired to the modem instead of using the built-in wi-fi.  That seems to tax the device a bit too much at times and cause issues like you're describing.  You may also be dealing with an overheating modem.