Srore [Translation - Downstream]

Versuchen Sie, die Konsole aus- und wieder einzuschalten. Halten Sie den Netzschalter an der Vorderseite der Konsole etwa 15 Sekunden lang gedrückt, bis die Betriebsanzeige erlischt. Warten Sie ungefähr 60 Sekunden und schalten Sie ihn dann wieder ein. Stellen
Sie sicher, dass Sie beim Einschalten der grünen Animationsanzeige "XBOX ONE" sehen. Rest Router auch den Versuch zu spielen

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[Mod Translation - Try switching the console off and on again.
Press and hold the power button on the front of the console for about 15 seconds until the power indicator turns off.
Wait about 60 seconds and then turn it back on.
Make sure you see "XBOX ONE" when you turn on the green animation screen.
Rest router also try to play]

The Xbox one does not support Dial up since it does not meet the minimum required speed/bandwidth for online play. That's why your Wifi works - that's most likely on cable or DSL that meets the minimum requirements. And if you are plugging the dial up jack
(RJ-22 connector) into your xbox, that will not work in any way, you must use the RJ-45 cable as that's what the xbox one supports. Regular Dial up is 56Kb/s download and the minimum for xbox live is 3Mb/s (3,000,00Kb/s). The upload speeds are also similar.

For more info on minimum required bandwidth and speeds see this page:

https://support.xbox.com/xbox-one/networking/slow-performance-solution

The way the One works is you put it between the upstream end and downstream end and it works with the set-top box. If the "set-top box" is downstream I doubt it works.

You don't you can buy it fromnthe retailer their own replacement warranty or goto your ms store link (not xbox store) as long as you are within the 30days of purchase that includes retailers

For ms srore you must upload the receipt since there are no longer any physical stores

And you have to be in a ms region

Downstream errors are usually server side - Have you tried a different browser to confirm?