Cant sign in with this error message displaying 0x8015dc16

Hi Charlie,

Thank you for posting on the Xbox forums. I'd be happy to help!

First, let's rule out network connection issues by unplugging your router and modem for a minimum of 5 minutes. Then go ahead and do a
hard restart and power cycle to the console. Hold down the power
button on the console for about 10 seconds until it shuts down and then remove the power cable from the Xbox and the power outlet for about 5 minutes. Then re-connect and wait 60 seconds before turning on the Xbox.

If that doesn't help, then I recommend removing your account from the Xbox and re adding the account then power cycle the Xbox again with the above steps.

1. Press the Xbox button to open the guide.
2. Select System > Settings > Account
   > Remove accounts.
3. Select the account that you want to remove, and then select Remove to confirm.
   
4. When you're finished, select Close.

To re-add the account,

1. Press the Xbox button to open the guide.
2. Scroll to the left corner of the screen, move all the way down and select
   Add new.

Let us know if this helps!

I had the same issue. I removed my account. Then did a hard reboot (pulled the pulg), added account back in...worked.

Same problem. None of the above works

Tengo el mismo problema ya hice todo lo que dices y no funciono volvi mi consola a estado de fabrica y al momento de introducir mi cuenta aparece lo mismo

I have the exact same issue. NOthing on that error code.