Xbox 360 can't connect to Xbox Live

I'm having trouble downloading my account to Xbox 360 for a few weeks now. The following situation perfectly describes my situation so I copied it. Does someone know what might fix this problem ?

Hello, I desperately need help as I'm about to throw my Xbox through my window...

So, I tried to play some Xbox 360 games on my Xbox One but it said I had no network and couldn't connect to Xbox live. I tried:

- Deleting and Reinstalling all the 360 games

- Wireless connection to router

- Wired connection to router

- Deleting Xbox One profile and redownloading

- Speaking to support

- Power cycling Xbox

- Restarting router

- Booting the game offline then going online

- Putting Xbox One IP in a DMZ

- Port forwarding (tricky btw)

and finally

- Cleared local 360 storage

Now here is the problem... it somehow managed to go and get worse...

I boot the game and get stuck at "Getting your Xbox 360 info..." and the progress bar doesn't fill up at all. Then after a while it completely fades to black and starts the game anyway but with no profile. There's no profiles on the 360 emulator (because I cleared the local 360 storage) and when I try to download a profile, it tells me it cannot connect to Xbox live and tells me to test my connection. Xbox live works absolutely fine and I'm connected to Xbox live on the Xbox One. What is going on???

I have looked EVERYWHERE online for this issue and there has been nothing to fix my issue apart from a console update a year ago which fixed the issue for some people but now its back. Please help, pleeease help me for the love of all that is good. I'm about to lose my mind.

:)