I noticed my phone was losing contacts' names in the Messaging app, so I signed out of my Hotmail account through the App Accounts settings page.
Now I am unable to retrieve any of the contacts associated with my account, through multiple restarts, attempts to sync, and deleting and re-adding this "Outlook Mail and Calendar" account, to no avail.
Most recently I keep getting an "Attention Required" alert in the People app for this account, but the phone's "fix" does nothing to fix sync. My contacts are all still present on Outlook on the web, but will no longer appear in my People app.
I'm on OS 14393.1715 (Lumia Icon); I am unable to update further through my settings app if that's a suggestion.