We're excited to announce that we've fully migrated the Xbox Forums to their new home, here on the Microsoft Community forums!
As of today, going to forums.xbox.com will redirect you here to the Xbox area of the Community forums. We've moved all of your existing threads over so you can continue and start conversations with the new forums experience.
We sincerely appreciate the feedback you have provided over this transition and can't wait for you to check out the new Xbox Forums!
Sorry to hear about the achievement issue. If your achievement is still not unlocked, I recommend checking to see if any other profiles on your console might have had the achievement unlocked under a different profile.
If you are certain that the achievement was not redeemed under another profile, I recommend trying a few troubleshooting steps to see if we can get this issue sorted.
Please give the following steps a try:
Press and hold the power button on your Xbox One console for 10 seconds.
Once you console is powered off, wait 5 minutes and then power on your console.
Check your achievements to see if the Day One achievement is unlocked.