Hey,
I had this problem since last year, but it seems I finally found a fix for it.
Tagging @Xyro69 as you had the same problem.
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Step
Go to window settings, then Games (Xbox symbol) then Xbox-Network and wait for it to show the "Xbox Live Multiplayer" Stuff -
Step
If you had the same problem as me it should show something like "not able to qualify" or "blocked"
There should be some links showing up with Xbox Troubleshooting guides, I recommend going through them first as they might fix the issue. They didn't for me -
Step
Check whether Teredo Filter is enabled in your Router.
I can only speak for Fritz Box, but you should find a guide for your router on the internet, too.
First, log in to your Fritz.Box by typing "fritz.box" in your browser search bar
Log in
Click the 3 dots in the top right and enabled "advanced Mode" or something like that
Go to Internet, then Filters then lists
Scroll down till you find something with "Teredo Filter"
Uncheck it
Save
These steps finally solved the problem for me and I hope they can help some of you out
