Teredo can't qualify. Windows 10?

As already mentioned in the title, I'm also "infected" with the Teredo problem.

I get this message under "Settings / Games / Xbox Network":

CONNECTION STATUS

Internet connection: Connected

Xbox Live Service: Running

POWER

Waiting time: 166ms

Package loss: 0%

XBOX LIVE MULTIPLAYER

NAT type: "Teredo can't qualify.

This could be you playing on

Multiplayer is a hindrance. "

Server connectivity: connected

I also tried to reset the router (to no avail).

Reinstalled the PC (without success).

I'm connected to the LAN.
No Wi-Fi adapter available.

Internet provider is Vodafone.

You probably have a Fritzbox, right?

Have a look on youtube at: teredo can't qualify.

There are very good solutions, as it is often not the same mistake.

Sometimes sas teredo needs to be reinstalled, sometimes it is blocked by the firewall, the best solution is to try it out