Why are my Xbox achievements not popping up?

Why are my Xbox achievements not popping up? If you completed the requirements to unlock the achievement on your console, but it doesn’t show, it might not be synchronized with the Xbox network. Allow up to 72 hours for this synchronization to take place.

If you completed the requirements to unlock the achievement on your console, but it doesn’t show, it might not be synchronized with the Xbox network. Allow up to 72 hours for this synchronization to take place.
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