I know that my internet is garbage, but I hoped I could test it like in the xbox PC...

Well, it could be just an instability with the service on the PC browsers, but I have tested here in my end, and it did work just fine with both browsers, since you're able to play on your iPhone, that's not the internet connection either, I could be a possible bug with your PC, somehow. I know you are probably on a working environment, but are you able to test it on another PC there?

> I hope you are kidding. Yes I know how to check my internet connection is up and working...

Some NAT problems are subtle and don't appear in the Test Xbox Live Connection test. Most likely there's a port blocked or misdirected away from your Xbox, in your router, modem, or at your ISP. Since the Xbox 360 uses different ports than PCs & Macs ordinarily
use, you can't see the effect of a port blockage except on the Xbox, for the NAT problem is really the blockage or misdirection of ports.

Perhaps you could confirm there's no port block with
http://canyouseeme.org instead?

yes, on both my modem and router there is a light indicating it can see it. however I tried to see if I could piggyback the internet from my PC, so tried to create a small network to do this, I made no changes to the cables, and set up this network not knowing
if anything was working, no new networks came up in my connections. But know my xbox is able to go past the network section of the XBL test and now cannont connect to the internet

I doubt it's my internet stability. My internet service has changed in a long time and this has been happening just for a few weeks. But I could try and measure the stability, I just don't know what I would have to do to conduct a test like that

Mister Mascot... i used Internet Explorer 10, 11 and Microsoft edge... even i used Firefox, Chrome and Opera on windows 7 and windows 10 and tested on an old win XP cpu too... on all cpus and browsers i got that issue with my account, but not with other
accounts...

But if i test it on the Web Browser of my Mobile phone, The Site WORKS PERFECT!

I dont know why i am getting that issue on all pcs i test even if i test on pcs from where i never logged in.

Hope this can help to solve my issue.

Thx a lot in advance.