Troubles began for OneDrive users on Sunday, December 17, 2017, at 3:36 PM UTC.
Screenshot-2017-12-18-Office-365-Service-Status-2-

If you've just tried to access your cloud storage and encountered an error, do not panic: it's not just you. OneDrive has been unavailable on desktops for several hours this Sunday.

A message was posted on their status website to acknowledge the issue.

Title: OneDrive web application issue
User Impact: Users may be unable to access the OneDrive web application located at https://onedrive.live.com.
More info: Affected users may encounter an error which states, "Sorry, an error has occurred". While we're focused on remediation, users may be able to access their files using the desktop or mobile clients as alternative methods.
Current status: We're investigating an issue with the OneDrive web application. We'll provide an update within 30 minutes.

Screenshot-2017-12-18--OneDrive-down-Current-outages-and-problems-

DownDetector comfirmed that the issue was quite widespread, as reports came from all over the world, mainly from the USA, Mexico, Europe and India.

Updates

Microsoft teams attempted to restart systems after analyzing the logs to find the source of the problem. Alas, rebooting the servers did not do the trick.

8PM Restarting affected systems did not completely resolve the issue. We're implementing a configuration update to restore

11:30 PM There was an issue that prevented the configuration update from deploying as expected. We've corrected the issue, and we're continuing with the deployment of the configuration update.