Teredo unable to qualify although I tried everything I could find online

Problem occured more than a month ago where I couldn't connect to any Xbox Live service, including Forza Horizon 4 online session. I tried some fixes and they worked, at least for a short while. 10 days ago, same problem occured again and since then, no
such solution could fix my problem. Here is the exact issue and the methods I tried

• NAT Type: Teredo is unable to qualify.
• Server Connectivity: Blocked

Type : enterpriseclient

Server Name : win1901.ipv6.microsoft.com.

Client Refresh Interval : 20 seconds

Client Port : unspecified

State : offline

Error : primary teredo server unreachable over UDP

Servername is obtained automatically by using "netsh int teredo set state servername=default" command

A quick note: I started to get the "primary teredo server unreachable over UDP" after some point. Once I started to get this error code, I tried port forwarding etc. Here are solutions I tried (not in the exact same order but I tried ones on official Microsoft
pages first):

• "Fix it" button under Settings>Gaming>Xbox Network

Everything on the following official Microsoft pages:

• https://beta.support.xbox.com/help/Hardware-Network/connect-network/server-connectivity-xbox-app-displays-blocked
• https://beta.support.xbox.com/help/Hardware-Network/connect-network/troubleshoot-party-chat

and followings from different pages

• Used gpedit (group policy editor) to force teredo to exist and have default servername (this one fixed my problem when it first occured but not this time, more
  info)
• Tried with different server names
• Did port forwarding in router interface
• Added new rule for port forwarding in the Windows Defender Firewall settings
• Tried each and every security option (enabling and disabling) in router settings
• Tried with a different internet and router
• Tried to connect using a different account on the same computer
• Tried to locate Teredo network adapter in device manager (it wasn't there and it never showed up under Microsoft brand when I tried to add it using Add Hardware Wizard)
• Troubleshooting in the settings
• Deleting and reinstalling all Xbox apps

Also, all drivers and Windows are up-to-date. I tried them individually, not in a row, and I paid attention to restart my computer after each solution. I also reset my router at some point but that did nothing as well. All of the settings under Windows
Security page is enabled and there seem to be no problem.

Today, like 2 hours ago, I did a clean Windows setup, formatted all disks, I updated all my drivers as well as Windows and guess what, Teredo still DOES NOT work. I tried the solutions on official Microsoft pages over again after clean start as well as
the reddit post I included above. I legitimately tried everything I could think of and found so far. At this point, I don't even know what to do. I thought about calling my ISP and shouting to their face but I don't think it is because of my ISP, if it was
then why teredo weren't working when I tried it on whole another internet and router? Please help

:)