Xbox one code displayed 0x801901f4.

Hello Best!

Thank you for posting on Xbox Forums! I understand that not being able to sign into your account can be frustrating but I will be happy to assist you today with the issue. As on of the ambassador's have previously mentioned, we would recommend trying
to
Power Cycle the console as a first step in troubleshooting. If that does not work, I would then suggest

Removing and Re-adding your account as there might be some corrupt data within the account preventing it from being signed in. Also, if this doesn't work, the next step would be to

Perform a Soft Factory Reset of the console, (Keep Games & Apps). If you have any further questions please feel free to reply back letting us know. Thank you again for posting on Xbox Forums!

Try performing a hard reset EXACTLY like this. Hold the power button on the console for 8 seconds or until the power shuts down completely.
Unplug the power cord from the back of the console for 5 minutes.
Plug the power cord back in and restart the console.

Some users from another post with this same error code said that removing the profile and re add it again seems to fix this issue. Let us know if it fixed.

I would start with a power cycle, reset your router, and try again,

Don't forget to check the https://support.xbox.com/en-US/xbox-live-status for status updates to see if Microsoft is having issues (at time of post, "Hello
Xbox members, we’re currently experiencing an issue. We apologize for the inconvenience. Please check back for updates.")

So the answer in this case is yes, Xbox is having sign in issues, please remain patient as they are aware of the issue and are working on the bugs

XBOX status or Twitter is your best friend when having sign in issues, definitely keeps you up to date on if there are issues on Microsofts end or yours.

Good luck

Do you happen to know when your subscription to Xbox Live expires?