When trying to unlock the achievement "Castaway" I am unable to unlock it. I have been eating nothing but kelp for over 3 minecraft days and still haven't unlocked the achievement.

When trying to unlock the achievement "Castaway" I am unable to unlock it. I have been eating nothing but kelp for over 3 Minecraft days and still haven't unlocked the achievement. I have relogged, checked the Xbox app to see if it was claimed and various other ways.